List of the Species or Varieties of Lepidoptera which, so far as at present known, are confined to the British Islands. (The figures show the dates when the species was first described. Species added since the first edition are marked with an asterisk.)

Diurni.

1. Polyommatus dispar. "The large copper." This fine insect, once common in the fens, but now extinct owing to extensive drainage, is generally admitted to be peculiar to our island, at all events as a variety or local form. Its continental ally differs constantly in being smaller and in having smaller spots; but the difference, though constant, is so slight that it is now classed as a variety under the name of rutilus. Our insect may therefore be stated to be a well-marked local form of a continental species.

2. Lycæna astrarche, var. artaxerxes. This very distinct form is confined to Scotland and the north of England. The species of which it is considered a variety (more generally known to English entomologists as P. agestis) is found in the southern half of England, and almost everywhere on the continent.

Bombyces.

3. Lithosia complana, var. sericea. North of England (1861).

4. Hepialus humuli, var. hethlandica. Shetland Islands (1865). A remarkable form, in which the male is usually yellow and buff instead of pure white, as in the common form, but exceedingly variable in tint and markings.

5. Epichnopteryx reticella. Sheerness, Gravesend, and other localities along the Thames (1847); Hayling Island, Sussex.

6. E. pulla, var. radiella. Near London, rare (1830?); the species in Central and Southern Europe. (Doubtfully peculiar in Mr. Stainton's opinion.)

Noctuæ.

7. Acronycta euphorbiæ, var. myricæ. Scotland only (1852). A melanic form of a continental species.

8. Agrotis subrosea. Cambridgeshire and Huntingdonshire fens, perhaps extinct (1835). The var. subcærulea is found in Finland and Livonia.

9. Agrotis candelarum var. ashworthii. South and West (1855). Distinct and not uncommon.

10. Luperina luteago, var. barretti. Ireland (1864).

11. Aporophyla australis, var. pascuea. South of England (1830). A variety of a species otherwise confined to South Europe.

12. Hydræcia nictitans, var. paludris.

Geometræ.

13. Boarmia gemmaria, var. perfumaria. Near London and elsewhere. A large dark variety of a common species.

14. *B. repandata, var. sodorensium. Outer Hebrides.

15. *Emmelesia albulata, var. hebridium. Outer Hebrides.

16. *E. albulata, var. thules. Shetland Islands.

17. *Melanippe montanata, var. shetlandica. Shetland Islands.

18. *M. sociata, var. obscurata. Outer Hebrides. A dark form.

19. Cidaria albulata, var. griseata. East of England (1835). A variety of a species otherwise confined to Central and Southern Europe.

20. Eupithecia constrictata.. Widely spread, but local (1835). Larva on thyme.

21. *E. satyrata, var. curzoni. N. Scotland.

22. *E. nanata var. curzoni. Shetland Islands.

Pyralidina.

23. Aglossa pinguinalis, var. streatfieldi. Mendip Hills (1830). A remarkable variety of the common "tabby."

24. *Scoparia cembræ, var. scotica. Scotland (1872).

25. *Myelois ceratoniæ, var. pryerella. North London (1871).

26. *Howœosoma nimbella, var. saxicola. England, Scotland, Isle of Man (1871).

27. *Epischnia bankesiella. Isle of Portland (1888).

Tortricina.

28. Aphelia nigrovittana. Scotland (1852). A local form of the generally distributed A. lanceolana.

29. Grapholita parvulana. Isle of Wight (1858). Rare. A distinct species.

30. Conchylis erigerana. South-east of England (1866).

31. *Brachytænia woodiana. Herefordshire (1882).

32. *Eupœcilia angustana, var. thuleana. Shetland Islands.

33. *Tortrix donelana. Connemara, Ireland (1890).

Tineina.

34. Tinea cochylidella. Sanderstead, near Croydon (1854). Unique!

35. Acrolepia betulætella. Yorkshire and Durham (1840). Rare.

36. Argyresthia semifusca. North and West of England (1829). Rather scarce. A distinct species.

37. Gelechia divisella. A fen insect (1856). Rare.

38. G. celerella. West of England (1854). A doubtful species.

39. *G. tetragonella. Yorkshire. Norfolk. Salt marshes.

40. *G. sparsiciliella. Pembroke.

41. *G. plantaginella. A salt-marsh species.

42. G. Ocellatella (Barrett nec Stainton). Bred from Beta maritima. Very distinct.

43. Bryotropha politella. Moors of North of England. Norfolk (1854).

44. *B. portlandicella. Isle of Portland (1890).

45. Lita fraternella. Widely scattered (1834). Larva feeds on shoots of Stellaria uliginosa in spring.

46. L. blandulella. Kent.

47. Anacampsis sircomella. North and West England (1854). Perhaps a melanic variety of the more widely spread A. tæniolella.

48. A. immaculatella. West Wickham (1834). Unique! A distinct species.

49. *Œcophora woodiella?

50. Glyphipteryx cladiella. Eastern Counties (1859). Abundant.

51. G. schœnicolella. In several localities (1859).

52. Gracilaria stramineella. (1850). On birch. Perhaps a local form of G. elongella, found on alder.

53. Ornix loganella. Scotland (1848). Abundant, and a distinct species.

54. O. devoniella. In Devonshire (1854). Unique!

55. Coleophora saturatella. South of England (1850). Abundant on broom.

56. C. inflatæ. South and East of England. On Silene inflata. ? continental.

57. C. squamosella. Surrey (1856). Very rare, but an obscure species.

58. C. salinella. On Sea-coast (1859). Abundant.

59. *C. potentillæ. South of England.

60. *C. adjunctella. Essex salt marshes. ? Lancashire (1882).

61. *C. limoniella. Isle of Wight. Feeds on Statice limonium.

62. Elachista flavicomella. Dublin (1856). Excessively rare, two specimens only known.

63. *E. scirpi. Wales and Sussex. Salt marshes.

64. E. consortella. Scotland (1854). A doubtful species.

65. E. megerlella. Widely distributed (1854). Common. Larva feeds in grass during winter and early spring.

66. E. obliquella. Near London (1854). Unique!

67. E. triseriatella. South of England (1854). Very local; an obscure species.

68. *Tinagma betulæ. East Dorset (1891).

69. Lithocolletis nigrescentella. Northumberland (1850). Rare; a dark form of L. Bremiella, which is widely distributed.

70. *L. anderidæ. Sussex. Dorset (1886).

71. L. irradiella. North Britain (1854). A northern form of the more southern and wide-spread L. lautella.

72. L. triguttella. Sanderstead, near Croydon (1848). Unique! very peculiar.

73. L. ulicicolella. In a few wide-spread localities (1854). A peculiar form.

74. L. caledoniella. North Britain (1854). A local variety of the more widespread L. corylifoliella.

75. L. dunningiella. North of England (1852). A somewhat doubtful species.

76. Bucculatrix demaryella. Widely distributed (1848). Rather common.

77. Trifurcula squamatella. South of England (1854). A doubtful species.

78. Nepticula ignobiliella. Widely scattered (1854). On hawthorn, not common. ? on continent.

79. N. poterii. South of England (1858). Bred from Larvæ in Poterium sanguisorba.

80. N. quinquella. South of England (1848). On oak leaves, very local. ? continental.

81. N. apicella. Local (1854). Probably confused with allied species on the continent.

82. N. headleyella. Local (1854). A rare species.

83. *N. hodgkinsoni. Lancashire.

84. *N. woolhopiella. Herefordshire.

85. *N. serella. Westmoreland and S. England.

86. *N. auromarginella. Dorset (1890).

87. *Micropteryx sangii. (1891).

88. *M. salopiella.

Pterophorina.

89. Agdistis bennetti. East coast. I. of Wight (1840). Common on Statice limonium.

We have here a list of eighty-nine species, which, according to the best authorities, are, in the present state of our knowledge, peculiar to Britain. It is a curious fact that no less than fifty of these have been described more than twenty-five years; and as during all that time they have not been recognised on the continent, notwithstanding that good coloured figures exist of almost all of them, it seems highly probable that many of them are really confined to our island. At the same time we must not apply this argument too rigidly, for the very day before my visit to Mr. Stainton he had received a letter from Professor Zeller announcing the discovery on the continent of a species of our last family, Pterophorina, which for more than forty years had been considered to be exclusively British. This insect, Platyptilia similidactyla (Pterophorus isodactylus, Stainton's Manual), had been taken rarely in the extreme north and south of our islands—Teignmouth and Orkney, a fact which seemed somewhat indicative of its being a straggler. Again, seven of the species are unique, that is, have only been captured once; and it may be supposed that, as they are so rare as to have been found only once in England, they may be all equally rare and not yet found on the continent. But this is hardly in accordance with the laws of distribution. Widely scattered species are generally abundant in some localities; while, when a species is on the point of extinction, it must for a time be very rare in the single locality where it last maintains itself. It is then more probable that some of these unique species represent such as are almost extinct, than that they have a wide range and are equally rare everywhere; and the peculiarity of our insular climate, combined with our varied soil and vegetation, offer conditions which may favour the survival of some species with us after they have become extinct on the continent.

Of the sixty-nine species recorded in my first edition fourteen have been since discovered on the continent, while no less than twenty-two species and eleven varieties have been added to the list. As we can hardly suppose continental entomologists to be less thorough collectors than ourselves, it ought to be more and more difficult to find any insects which are unknown on the continent if all ours really exist there; and the fact that the list of apparently peculiar British species is an increasing one renders it probable that many of them are not only apparently but really so. Both general considerations dependent on the known laws of distribution, and the peculiar habits, conspicuous appearance, and restricted range, of many of our species, alike indicate that some considerable proportion of them will remain permanently as peculiar British species.

We will now pass on to the Coleoptera, or beetles, an order which has been of late years energetically collected and carefully studied by British entomologists.

List of the Species and Varieties of Beetles which, so far as at present known, are confined to the British Islands. Those added since the first edition are marked with an asterisk.

Carabidæ.

1. *Bembidium saxatile, var. vectensis (Fowler). Isle of Wight.

2. Dromius vectensis (Rye). Common in the Isle of Wight, also in Kent, and at Weymouth and Seaton. Closely allied to D. sigma.

3. Harpalus latus, var. metallescens (Rye). Unique, but very marked! South coast. "Perhaps a sport or a hybrid" (Fowler).

4. Acupalpus derelictus (Dawson). Unique! North Kent. Canon Fowler thinks it may be a variety of A. dorsalis.

Dyticidæ.

5. *Acilius sulcatus, var. scoticus (Curtis). Scotland. A melanic variety.

Helophoridæ.

6. Ochthebius poweri (Rye). Very marked. S. coast. A few specimens only.

7. *O. æneus (Steph).

Brachyelytra.

8. Ocyusa hibernica (Rye). Ireland, mountain tops, and at Braemar.

9. *Oxypoda tarda (Sharp).

10.         ,,       pectita (Sharp). Scotland.

11.         ,,       verecunda (Sharp). Scotland, also London districts.

12. Homalota diversa (Sharp).

13.         ,,        fulvipennis (Rye).

14.         ,,        oblongiuscula (Sharp). Scotland, also England and Ireland.

15.         ,,        princeps (Sharp). A coast insect.

16.         ,,        curtipennis (Sharp). Scotland and near Birmingham.

17. H. levana, var. setigera (Sharp).

18. Stenus oscillator (Rye). Unique! South coast. May be a hybrid.

19. Trogophlæus spinicollis (Rye). Mersey estuary, unique! Most distinguishable, nothing like it in Europe. Perhaps imported from another continent.

20. Eudectus whitei (Sharp). Scotch hills. A variety of E. Giraudi of Germany (the only European species) fide Kraatz (Sharp).

21. Homalium rugulipenne (Rye). Exceedingly marked form. Northern and western coasts; rare.

22. *Mycetoporus monticola (Fowler). Cheviots and Inverness-shire.

Scydmænidæ.

23. *Scydmænus poweri (Fowler) S. England. A recent discovery.

24. *S. planifrons (Fowler).                    ,,                    ,,

Pselaphidæ.

25. Bryaxis cotus (De Sauley). Scotland.

26. Bythinus glabratus (Rye). Sussex coast; also Isle of Wight; a few specimens; very distinguishable; myrmecophilous (lives in ants' nests).

Trichopterygidæ.

27. Ptinella maria                    (Matthews) Derbyshire.

28. Trichopteryx saræ             (      ,,      ) Notts.

29.           ,,            poweri          (      ,,      ) Oxon.

30.           ,,            edithia          (      ,,      ) Kent.

31.           ,,          *angusta        (      ,,      ) Leicestershire.

32.           ,,            kirbii            (      ,,      ) Norfolk.

33.           ,,            fratercula  (      ,,      )

34.           ,,            waterhousii (      ,,      )

35.           ,,            championis   (      ,,      ) Wicken Fen.

36.           ,,            jansoni         (      ,,      ) Leicestershire.

37.           ,,            suffocata (Haliday). Ireland, Co. Cork.

38.           ,,            carbonaria (Matthews). Notts.

39. Ptilium halidayi (Matthews). Sherwood Forest.

40.       ,,      caledonicum (Sharp). Scotland; very marked form.

41.       ,,      insigne (Matthews). London district.

42. *Orthoperus mundus (Matthews). Oxfordshire.

43. *O. punctulatus (Matthews). Lincolnshire.

Anisotomidæ.

44. Agathidium rhinoceros (Sharp). Old fir-woods in Perthshire; local, many specimens; a very marked species.

45. Anisotoma similata (Rye). South of England. Two specimens.

46.          ,,         lunicollis (Rye). North-east and South of England, a very marked form; several specimens.

Phalacridæ.

47. Phalacrus brisouti (Rye). South of England. Rare. "Perhaps a small form of P. coruscus" (Fowler).

Cryptophagidæ.

48. Atomaria divisa (Rye). Unique! South of England.

Lathridiidæ.

49. Melanopthalma transversalis, var. wollastoni (Waterhouse). South coast, and Lincolnshire.

Byrrhidæ.

50. Syncalypta hirsuta (Sharp). South of England, local. "Closely allied to S. setigera" (Fowler).

Mordellidæ.

51. *Anaspis septentrionalis. Scotland (1891). (Champion.)

52. *       ,,     garneysi (Fowler). London District. (1890.)

Telephoridæ.

53. Telephorus darwinianus (Sharp). Scotland, sea-coast. A stunted form of abnormal habits. Perhaps a variety of T. lituratus.

Cyphonidæ.

54. Cyphon punctipennis (Sharp). Scotland.

Anthicidæ.

55. Anthicus salinus (Crotch). South coast.

56.        ,,        scoticus (Rye). Loch Leven; very distinct; many specimens.

Cioidæ.

57. *Cis bilamellatus (Wood). West Wickham, Kent. "Perhaps imported. Has the appearance of an exotic Cis" (Fowler).

Tomicidæ.

58. *Pityopthorus lichtensteinii, var. scoticus (Blandford). Scotland.

Curculionidæ.

59. Ceuthorhynchus contractus, var. pallipes (Crotch). Lundy Island; several specimens. A curious variety only known from this island.

60. Liosomus troglodytes (Rye). A very queer form. Two or three specimens. South of England.

61. *Orcheites ilicis, var. nigripes (Fowler). London District. (1890.)

62. Apion ryei (Blackburn). Shetland Islands. Several specimens. Perhaps a var. of A. fagi.

Chrysomelidæ.

63. Chrysomela staphylea, var. sharpi (Fowler). Solway district.

Halticidæ.

64. Longitarsus agilis (Rye). South of England; many specimens.

65.           ,,          distinguenda (Rye). South of England; many specimens.

66. Psylliodes luridipennis (Kutschera). Lundy Island. A very curious form, not uncommon in this small island, to which it appears to be confined. "An extreme and local variety of P. chrysocephala" (Fowler).

Coccinellidæ.

67. Scymnus lividus (Bold). Northumberland. A doubtful species.

Of the sixty-seven species and varieties of beetles in the preceding list, a considerable number no doubt owe their presence there to the fact that they have not yet been discovered or recognised on the continent. This is almost certainly the case with many of those which have been separated from other species by very minute and obscure characters, and especially with the excessively minute Trichopterygidæ described by Mr. Matthews. There are others, however, to which this mode of getting rid of them will not apply, as they are so marked as to be at once recognised by any competent entomologist, and often so plentiful that they can be easily obtained when searched for. The peculiar species of Apion in the Shetland Islands is interesting, and may be connected with the very peculiar climatal conditions there prevailing, which have led in some cases to a change of habits, so that a species of weevil (Otiorhynchus maurus) always found on mountain sides in Scotland here occurs on the sea-shore. Still more curious is the occurrence of two distinct forms (a species and a well-marked variety) on the small granitic Lundy Island in the Bristol Channel. This island is about three miles long and twelve from the coast of Devonshire, consisting mainly of granite with a little of the Devonian formation, and the presence here of peculiar insects can only be due to isolation with special conditions, and immunity from enemies or competing forms. When we consider the similar islands off the coast of Scotland and Ireland, with the Isle of Man and the Scilly Islands, none of which have been yet thoroughly explored for beetles, it is probable that many similar examples of peculiar isolated forms remain to be discovered.

Looking, then, at what seem to me the probabilities of the case from the standpoint of evolution and natural selection, and giving due weight to the facts of local distribution as they are actually presented to us, I am forced to differ from the opinion held by our best entomological authorities, and to believe that some at least, perhaps many, of the species which, in the present state of our knowledge, appear to be peculiar to our islands, are, not only apparently, but really, so peculiar.

I am indebted to Mr. Robert McLachlan for the following information on certain Trichopterous Neuroptera (or caddis-flies) which appear to be confined to our islands. The peculiar aquatic habits of the larvæ of these insects, some living in ponds or rivers, others in lakes, and others again only in clear mountain streams, render it not improbable that some of them should have become isolated and preserved in our islands, or that they should be modified owing to such isolation.

Trichoptera peculiar to the British Isles.

1. Philopotamus insularis. (? A variety of P. montanus.)—This can hardly be termed a British species or variety, because, so far as at present known, it is peculiar to the Island of Guernsey. It agrees structurally with P. montanus, a species found both in Britain and on the continent, but it differs in its strikingly yellow colour, and less pronounced markings. All the specimens from Guernsey are alike, and resident entomologists assured Mr. McLachlan that no other kind is known. Strange to say, some examples from Jersey differ considerably, resembling the common European and British form. Even should this peculiar variety be at some future time found on the continent it would still be a remarkable fact that the form of insect inhabiting two small islands only twenty miles apart should constantly differ; but as Jersey is between Guernsey and the coast, it seems just possible that the more insular conditions, and perhaps some peculiarity of the soil and water in the former island, have really led to the production or preservation of a well-marked variety of insect. In the first edition of this work two other species were named as then, peculiar to Britain—Setodes argentipunctella and Rhyacophila munda, but both have now been taken on the continent.

2. Mesophylax impunctatus, var. zetlandicus.—A variety of a South and Central European species, one specimen of which has been found in Dumfriesshire. The variety is distinguished by its small size and dark colour.

Land and Freshwater Shells.—In the first edition of this work four species were noted as being, so far as was then known, exclusively British. Two of these, Cyclas pisidioides (now called Sphærium pisidioides) and Geomalacus maculosus, have been discovered on the continent, but the other two remain still apparently confined to these islands; and to these another has been added by the discovery of a new species of Hydrobia in the estuary of the Thames. The peculiar species now stands as follows:—

1. Limnea involuta.—A pond snail with a small polished amber-coloured shell found only in a small alpine lake and its inflowing stream on Cromagloun mountain near the lakes of Killarney. It was discovered in 1838, and has frequently been obtained since in the same locality. It is sometimes classed as a variety of Limnea peregra, and is at all events closely allied to that species.

2. Hydrobia jenkinsii.—A small shell of the family Rissoidæ inhabiting the Thames estuary both in Essex and Kent. It was discovered only a few years ago, and was first described in 1889.

3. Assiminea grayana.—A small estuarine pulmonobranch found on the banks of the Thames between Greenwich and Gravesend, on mud at the roots of aquatic plants. It has been discovered more than sixty years.

But besides the above-named species there are a considerable number of well-marked varieties of shells which seem to be peculiar to our islands. A list of these has been kindly furnished me by Mr. Theo. D. A. Cockerell, who has paid much attention to the subject; and after omitting all those whose peculiarities are very slight or whose absence from the continent is doubtful, there remain a series of forms some of which are in all probability really endemic with us. This is the more probable from the fact that an introduced colony of Helix nemoralis at Lexington, Virginia, presents numerous varieties among which are several which do not occur in Europe.^[136] The following list is therefore given in the hope that it may be useful in calling attention to those varieties which are not yet positively known to occur elsewhere than in our islands, and thus lead, ultimately, to a more accurate knowledge of the facts. It is only by obtaining a full knowledge of varieties, their distribution and their comparative stability, that we can ever hope to detect the exact process by which nature works in the formation of species.

List of the Species and Varieties of Land and Freshwater Shells which, so far as at present known, are believed to be Peculiar to the British Isles or not found on the Continent.

Limacidæ.

1. Limax marginatus, var. maculatus. Ireland; frequent, very distinct.

2.     ,,           ,,          ,,   decipiens. Ireland and England.

3.     ,,      flavus, var. suffusus. England; Melanic form.

4.     ,,          ,,      ,,   griseus. England; Melanic form.

5. Agriolimax agrestis, var. niger. Yorkshire. Melanic. Azores.

6.        ,,            ,,        ,,   griseus. England. Melanic.

7. Amalia gagates, var. rava. W. of England.

8.      ,,    sowerbyi, var. rustica. England.

9.      ,,          ,,         ,,   nigrescens. Surrey and Middlesex.

10.    ,,          ,,         ,,   bicolor. Ealing.

11. Hyalina crystallina, var. complanata. Near Bristol.

12.      ,,     fulva, var. alderi.

13. Vitrina pellucida, var. depressiuscula. S. England, Wales.

Helicidæ.

14. Arion ater, var. albo-lateralis. England, Wales, Isle of Man; very distinct.

15.    ,,    hortensis, var. fallax. England. Common at Boxhill.

16. Geomalacus maculosus. Kerry and Cork. Three varieties have been described, one of which occurs in Portugal.

17. Helix aspersa, var. lutescens. England. Not rare perhaps in France.

18.    ,,    nemoralis, var. hibernica. Ireland.

19.    ,,    rufescens, var. manchesteriensis. England.

20.    ,,    hispida, var. subglobosa. England.

21.    ,,        ,,        ,,   depilata. England.

22.    ,,        ,,        ,,   minor. England, Ireland.

23.    ,,    granulata, var. cornea. Lulworth, Dorset.

24.    ,,    virgata, var. subaperta. Bath.

25.    ,,        ,,        ,,   subglobosa. England, Wales, Bantry Bay.

26.    ,,        ,,        ,,   carinata. Wareham, Dorset.

27.    ,,    caperata, var. major. England, Wales, Scotland. Distinct.

28.    ,,          ,,        ,,   nana. England.

29.    ,,          ,,        ,,   subscalaris. Wales, Ireland.

30.    ,,          ,,        ,,   alternata. England, Kent.

31.    ,,    acuta, var. nigrescens. England.

Pupidæ.

32. Pupa anglica, var. pallida. Not rare.

33.    ,,    lilljeborgi, var. bidentata. Ireland.

34.    ,,    pygmea, var. pallida. Dorset and Devon.

35. Clausilia rugosa, var. parvula. Ireland.

Stenogyridæ.

36. Cochlicopa lubrica, var. hyalina. Wales, Scotland.

37. Cœcilianella acicula, var. anglica. England.

Succineidæ.

38. Succinea putris, var. solidula. Wiltshire.

39.      ,,       virescens, var. aurea. Ireland.

40.      ,,       pfeifferi,     ,,   rufescens. England, Ireland.

41.      ,,            ,,          ,,   minor. England.

Limnæidæ.

42. Planorbis fontanus, var. minor. England.

43.      ,,       carinatus,   ,,   disciformis. England.

44.      ,,       contortus,  ,,   excavatus. Ireland.

45.      ,,            ,,         ,,   minor.

46. Physa fontinalus, var. oblonga. England, Wales, Ireland.

47. Limnæa involuta. Ireland.

48. Limnæa glutinosa, var. mucronata.

49.      ,,      peregra, var. burnetti. Scotland. Very distinct.

50.      ,,           ,,       ,,   lacustris. Perhaps in C. Verde Islands.

51.      ,,           ,,       ,,   maritima. Great Britain.

52.      ,,           ,,       ,,   lineata. England.

53.      ,,           ,,       ,,   stagnaliformis. England.

54.      ,,      stagnalis, var. elagantula. Curious. In a pond at Chislehurst.

55.      ,,      palustris, var. conica. England, Ireland.

56.      ,,            ,,        ,,   tincta. England, Wales.

57.      ,,            ,,        ,,   albida. England.

58.      ,,      truncatula, var. elegans. England, Ireland. Distinct.

59.      ,,             ,,         ,,   fusca. Wales.

60. Ancylus lacustris, var. compressus. England.

Paludinidæ.

61. Paludina vivipara, var. efasciata. England. Not uncommon.

62.       ,,          ,,        ,,   atropurpurea. Pontypool.

Rissoidæ.

63. Hydrobia jenkinsii. Thames Estuary.

64.        ,,        ventrosa, var. minor.

65.        ,,             ,,         ,,   decollata.

66.        ,,             ,,         ,,   ovata.

67.        ,,             ,,         ,,   elongata.

68.        ,,             ,,         ,,   pellucida.

Cyrenidæ.

69. Sphærium corneum, var. compressum.

70.        ,,            ,,         ,,   minor.

71.        ,,            ,,         ,,   stagnicola.

72.        ,,      ovale, var. pallidum. England.

73.        ,,      lacustre, var. rotundum. Wales.

74. Pisidium pusillum, var. grandis.

75.       ,,          ,,         ,,   circulare. Wales.

76.       ,,     nitidum, var. globosum.

Unionidæ.

77. Unio tumidus, var. richensis. Regent's Park. Peculiar form.

78.    ,,   pictorum, var. latior. England.

79.    ,,       ,,          ,,   compressus. England.

80.    ,,   margaritifer, var. olivaceus.

81. Anodonta cygnæa, var. incrassata. England.

82.        ,,           ,,        ,,   pallida. England, Ireland.

Estuarine or Marine Pulmonotranchs.

83. Assiminea grayana. Thames Estuary.

Peculiarities of the British Flora.—Thinking it probable that there must also be some peculiar British plants, but not finding any enumeration of such in the British Floras of Babington, Hooker, or Bentham, I applied to the greatest living authority on the distribution of British plants—the late Mr. H. C. Watson, who very kindly gave me the information I required, and I cannot do better than quote his words: "It may be stated pretty confidently that there is no 'species' (generally accepted among botanists as a good species) peculiar to the British Isles. True, during the past hundred years, nominally new species have been named and described on British specimens only, from time to time. But these have gradually come to be identified with species described elsewhere under other names—or they have been reduced in rank by succeeding botanists, and placed or replaced as varieties of more widely distributed species. In his British Rubi Professor Babington includes as good species, some half-dozen which he has, apparently, not identified with any foreign species or variety. None of these are accepted as 'true species,' nor even as 'sub-species' in the Students' Flora, where the brambles are described by Baker, a botanist well acquainted with the plants of Britain. And as all these nominal species of Rubi are of late creation, they have truly never been subjected to real or critical tests as 'species.'"

In my first edition I was only able to name four species, sub-species, or varieties of flowering plants which were believed to be unknown on the continent. But much attention has of late years been paid to the critical examination of British plants in comparison with continental specimens, and I am now enabled to give a much more extensive list of the species or forms which at present seem to be peculiar. For the following list I am primarily indebted to Mr. Arthur Bennett of Croydon. Sir Joseph Hooker has been so kind as to examine it carefully and to give me his conclusions on the relative value of the differences of the several forms, and Mr. Baker, of Kew, has also assisted with his extensive knowledge of British plants.

List of Species, Sub-species, and Varieties of Flowering Plants found in Great Britain or Ireland, but not at present known in Continental Europe. By Arthur Bennett, F.L.S. The most distinct and best determined forms are marked with an asterisk.

1. *Caltha radicans (Forst.). "A much disputed species, or form of C. palustris. It is a relatively rare plant." (J. D. H.) "Certainly distinct from the Scandinavian form." (Ar. Bennett.)

2. *Arabis petræa (Lam.) var. grandifolia (Druce). Scotch mountains. "The larger flowers alone distinguish this." (J. D. H.)

3. Arabis ciliata (R. Br.). In Nyman's Conspectus Floræ Europææ this species is given as found in England and Ireland only. "A very much disputed form of a plant of very wide distribution in Europe and North America." (J. D. H.)

4. Brassica monensis (Huds.). "This and the continental B. cheiranthus (also found in Cornwall) are barely distinguishable from one another." (J. D. H.)

5. Diplotaxis muralis (D. C.) var. Babingtonii (Syme). South of England. "A biennial or perennial form; considered to be a denizen by Watson." (J. D. H.)

6. *Helianthemum guttatum (Mill), var. Breweri (Planch). Anglesea. "Very doubtful local plant. H. guttatum (true) has lately been found in the same locality." (J. D. H.)

7. *Polygala vulgaris (L.), var. grandiflora (Bab). Sligo, Ireland. "A very distinct variety." (J. D. H.)

8. Viola lutea (Huds.), var. amœna (Symons). "V. lutea itself is considered to be a form of V. tricolor, and V. amœna the better coloured of the two forms of V. lutea." (J. D. H.)

9. *Cerastium arcticum (Lange), var. Edmonstonii (Beeby). Shetland Is. "But C. arcticum is referable to the very variable C. alpinum." (J. D. H.) "Near to the European C. latifolium." (Ar. Bennett.)

10. *Geranium sanguineum (L.), var. Lancastriense (With.). Lancashire. "A prostrate local form growing out of its native soil in sand by the sea." (J. D. H.) Mr. Bennett writes: "I have grown G. sanguineum and its prostrate variety in sand, and neither became Lancastriense."

11. Genista tinctoria (L.), var. humifusa (Dickson). Cornwall. "A decumbent hairy form confined to the Lizard." (J. D. H.)

12. Cytisus scoparius (Link.), var. prostratus (Bailey). Cornwall. "A prostrate form." (J. D. H.)

13. Anthyllis vulneraria (L.), var. ovata (Bab.). Shetland Is. "A slight variety." (J. D. H.)

14. *Trifolium repens (L.), var. Townsendii (Bab.). Scilly Isles. "A well-marked form by its rose-purple flowers. Confined to the Scilly Isles." (J. D. H.)

15. *Rosa involuta (Sm.), var. Wilsoni. (Borrer.) Wales. "There are a multitude of forms or varieties of R. involuta, and R. wilsoni is one of the best-marked, found on the Menai Straits and Derry." (J. D. H.)

16. Rosa involuta var. gracilis (Woods). "This is considered by many as one of the commonest forms of R. involuta." (J. D. H.)

17. Rosa involuta var. Nicholsoni (Crepin). "Another slight variety of R. involuta." (J. D. H.)

18. Rosa involuta var. Woodsiana (Groves). "A Wimbledon Common variety of R. villosa." (J. D. H.)

19. Rosa involuta var. Grovesii (Baker). "Mr. Baker thinks this of no account." (J. D. H.)

20. Rubus echinatus (Lind.). "A variety of the widely spread R. Radula, itself a form of R. fruticosus." (J. D. H.)

21. *Rubus longithyrsiger (Lees). "Mr. Baker informs me that this is a very distinct plant never yet found on the continent." (J. D. H.)

22. Pyrus aria (Sm.) var. rupicola (Syme). "A very local form, confined to Gt. Britain, and owing its characters to its starved position." (Baker.)

23. Callitriche obtusangula (Le Gall), var. Lachii (Warren). Cheshire. "This is intermediate between two sub-species of C. verna." (J. D. H.)

24. *Œnanthe fluviatilis (Coleman). South of England. "The fluitant form of Æ. Phellandrium." (J. D. H.)

25. Anthemis arvensis (L.), var. anglica (Spreng). N. Coast of England. "A maritime form with more fleshy leaves formerly found near Durham. It has other very trifling characters." (J. D. H.)

26. Arctium intermedium (Bab.). "There are two sub-species of A. lappa, majus and minus, each with varieties, and this is one of the intermediates." (J. D. H.)

27. Hieracium holosericium (Backh.). Scotch Alps.

28. H. gracilentum (Backh.).                     ,,

29. H. lingulatum (Backh.).                       ,,       A var. of this in Scandinavia.

30. H. senescens (Backh.).                       ,,

31. H. chrysanthenum (Backh.).               ,,

32. H. iricum (Fr.). Teesdale and Scotland.

33. H. gibsoni (Backh.). Yorkshire and Westmoreland.

34. Hieracium nitidum (Backh.). Lower glens of the Scotch Alps. Mr. Bennett writes:—"The following Hieracia have been named by Mr. F. J. Hanbury as endemic forms. One can only safely say they are certainly not known in Scandinavia, as they have all been submitted to Dr. Lindeberg. But usually Scotch species are not represented in Central Europe to any great extent, though several do occur. Still these new forms ought to be critically compared with all Dr. Peters' new species."

35. H. Langewellense (Hanb.). Caithness.

36. H. pollinarium (Hanb.). Sutherland.

37. H. scoticum (Hanb.). Sutherland and Caithness.

38. H. Backhousei (Hanb.). Aberdeen, Banff, Inverness.

39. H. caledonicum (Hanb.). Caithness and Sutherland.

40. H. Farrense (Hanb.). Sutherland and Shetland Is.

41. H. proximum (Hanb.). Caithness. With regard to all these Hieracia Sir Joseph Hooker and Mr. Baker say:—"No case can be made of these. They are local forms with the shadowest of shady characters." Mr. Bennett writes: "H. iricum and H. Gibsoni are the best marked forms."

42. *Campanula rotundifolia (L.), var. speciosa (A. G. More). W. Ireland. "Very well distinguished by its large flowers and small calyx lobes, approaching the Swiss C. Scheuzeri." (J. D. H.)

43. Statice reticulata (Sm.). "Baker agrees with me that this is also a Mediterranean species." (J. D. H.)

44. Erythræa capitata (Willd.), var. sphærocephala (Towns.). Isle of Wight. "A form of E. centaurium utterly anomalous in its genus in the insertion of the stamens. A monster rather than a species." (J. D. H.)

45. *Erythræa latifolia (Sm.). On the sandy dunes near Liverpool. "A local form." (J. D. H.)

46. Myosotis collina (Hoffim.), var. Mittenii (Baker). Sussex.

47. Veronica officinalis (L.), var. hirsuta (Hopk.). Ayr, Scotland.

48. Veronica arvensis (L.), var. eximia (Towns.). Hampshire.

49. Mentha alopecuroides (Hull). Nearest to M. dulcissima (Dum.).

50. Mentha pratensis (Sole). Only once found.

51. Chenopodium rubrum (L.), var. pseudobotryoides (H. C. Watson).

52. Salix ferruginea (Forbes). England, Scotland. "Probably a hybrid between S. viminalis and S. cinerea." (J. D. H.)

53. Salix Grahami (Borr.). Sutherland, Perth. "A hybrid?" (J. D. H.)

54. Salix Sadleri (Syme). Aberdeen. "A hybrid?" (J. D. H.)

55. *Spiranthes Romanzoviana (Cham.). Ireland (N. America).

56. *Sisyrinchium angustifolium (Mill.). Ireland. (Arctic and Temp. N. America.)

57. Allium Babingtonii (Borrer). West England, West Ireland. "A form of A. ampeloprasum, itself a naturalised species." (J. D. H.)

58. *Potamogeton lanceolatus (Sm.). Anglesea, Cambridgeshire, Ireland. Mr. Bennett writes:—"Endemic! I have taken a good amount of trouble to ascertain this. Nearly 400 specimens I have distributed all over the world with requests for information as to anything like it. The response is everywhere the same, 'nothing.' The nearest to it occurs in the Duchy of Lauenberg but is referable to P. heterophyllus."

59. Potamogeton Griffithii (Ar. Bennett). Carnarvon. "Nearest to this is a probable hybrid from N. America, but not identical." (Ar. Bennett.)

60. Potamogeton pusillus (L.), sub-sp. Sturrockii (Ar. Benn.). Perth.

61. Potamogeton pusillus (L.), var. rigidus (Ar. Benn.). Orkneys, Shetlands.

62. Ruppia rostellata (Koch.), var. nana (Bosw.). Orkneys.

63. *Eriocaulon septangulare (With.). Hebrides, Ireland. N. America.

64. Scirpus uniglumis (Link), var. Watsoni (Bab.). Scotland, England. "This is a variety of a sub-species of the common S. palustris." (J. D. H.)

65. Luzula pilosa (Willd.), var. Borreri (Bromf).

66. *Carex involuta (Bab.). Cheshire. "A distinct enough plant but probably a hybrid between C. vesicaria and C. ampullacea, found in one place only." (J. D. H.)

67. Carex glauca (Murr.), var. stictocarpa (Sm.). Scotland.

68. Carex precox (Jacq.), var. capitata (Ar. Benn.). Ireland. "A remarkable plant (monstrosity?) simulating C. capitata (L.)." (Ar. Bennett.)

69. *Carex Grahami (Boott). "A mountain form of C. vesicaria." (J. D. H.)

70. *Spartina Townsendi (Groves). Hampshire. "A distinct but very local form of S. stricta, found in one place only." (J. D. H.)

71. Agrostis nigra (With.).

72. Deschampsia flexuosa (Trin.), var. Voirlichensis (J. C. Melvill). Perth.

73. *Deyeuxia neglecta (Kunth), var. Hookeri (Syme). Ireland. "A distinct variety confined to Lough Neagh." (J. D. H.)

74. Glyceria maritima (Willd.), var. riparia (Towns.). Hampshire.

75. Poa Balfouri (Bab.). Scotland. "An alpine sub-variety of a variety of the protean P. nemoralis." (J. D. H.)

In his comments on this extensive list of supposed peculiar British plants, Sir Joseph Hooker arrives at the following conclusions:—

1. There are four unquestionably distinct species which do not occur in continental Europe: viz.—

One absolutely endemic species, Potamogeton lanceolatus.

Three American species, Sisyrinchium angustifolium, Spiranthes romanzoviana, Eriocaulon septangulare.

2. There are sixteen endemic varieties of British species, viz.—

Eleven of more or less variable species, Caltha palustris, var. radicans; Polygala vulgaris, var. grandiflora; Cerastium arcticum, var. edmonstonii; Trifolium repens, var. Townsendii; Rosa involuta, var. wilsoni; Rubus fruticosus, sub-sp. longithyrsiger; Campanula rotundifolia, var. speciosa; Erythræa centaurium, sub-sp. latifolia; Carex involuta, (? Hyb.); Carex vesicaria, var. Grahami; Deyeuxia neglecta, var. Hookeri.

Five of comparatively well limited species. Arabis petræa, var. grandifolia; Helianthemum guttatum, var. Breweri; Geranium sanguineum, var. Lancastriense; Œnanthe Phellandrium, var. fluviatilis; Spartium stricta, var. Townsendi.

The above twenty species are marked in the list with an asterisk. Of the remaining fifty-five, Sir Joseph Hooker says, "that for various reasons it would not be safe to rely on them as evidence. In most cases the varietal form is so very trifling a departure from the type that this may be safely set down to a local cause, and is probably not constant. In others the plant is doubtfully endemic; in still others a hybrid."

Even should it ultimately prove that of the whole number of the fifty-five doubtful forms none are established as peculiar British varieties, the number admitted after so rigorous an examination is about what we should expect in comparison with the limited amount of speciality we have seen to exist in other groups. The three American species which inhabit the extreme west and north-west of the British Isles, but are not found on the continent of Europe are especially interesting, because they demonstrate the existence of some peculiar conditions such as would help to explain the presence of the other peculiar species. Whether we suppose these American forms to have migrated from America to Europe before the glacial epoch, or to be the remnants of a vegetation once spread over the north temperate zone, we can only explain their presence with us and not further east by something favourable either in our insular climate or in the limited competition due to our comparative poverty in species.

About half of the peculiar forms are found in the extreme west or north of Britain or in Ireland, where peculiar insular conditions are at a maximum; and the influence of these conditions is further shown by the number of species of West or South European plants which occur in the same districts.

We may here notice the interesting fact that Ireland possesses no less than twenty species or sub-species of flowering plants not found in Britain, and some of these may be altogether peculiar. As a whole they show the effect of the pre-eminently mild and insular climate of Ireland in extending the range of some south European species. The following list of these plants, for which I am indebted to Mr. A. G. More, with a few remarks on their distribution, will be found interesting:—

List of Irish Flowering Plants which are not found in Britain.

1. Polygala vulgaris (var. grandiflora). Sligo.

2. Campanula rotundifolia (var. speciosa). W. Ireland.

3. Arenaria ciliata. W. Ireland (also Auvergne, Pyrenees, Crete).

4. Saxifraga umbrosa. W. Ireland (also Pyrenees, N. Spain, Portugal).

5.        ,,      geum. S. W. Ireland (also Pyrenees).

6.        ,,      hirsuta. S. W. Ireland (also Pyrenees).

7. Inula salicina. W. Ireland (Scandinavia, Middle and South Europe).

8. Erica mediterranea. W. Ireland (W. France, Spain, Portugal).

9.     ,,   mackaiana (tetralix sub.-sp.) W. Ireland (Spain).

10. Arbutus unedo. S. W. Ireland (W. of France, Spain, Portugal and shores of Mediterranean).

11. Dabeocia polifolia. W. Ireland (W. of France, Spain and Portugal).

12. Pinguicula grandiflora. S. W. Ireland (Spain, Pyrenees, Alps of France and Switzerland).

13. Neotinea intacta. W. Ireland (S. France, Portugal, Spain, and shores of Mediterranean).

14. Spiranthes romanzoviana. S. W. Ireland (North America).

15. Sisyrinchium angustifolium. W. Ireland (North America, Arctic and Temp.).

16. Potamogeton lonchites. Ireland, Mr. Arthur Bennett informs me that this is certainly not British or European, but may possibly be identical with P. fluitans var. Americanus of the U. States.

17. Potamogeton kirkii (natans sub.-sp.). W. Ireland. (Arctic Europe?)

18. Eriocaulon septangulare. W. Ireland, Skye, Hebrides (North America).

19. Carex buxbaumii. N. E. Ireland, on an island in Lough Neagh (Arctic and Alpine Europe, North America).

20. Deyeuxia neglecta (var. Hookeri). On the shores and islands of Lough Neagh. (And in Germany, Arctic Europe, and North America.)

We find here nine south-west European species which probably had a wider range in mild preglacial times, and have been preserved in the south and west of Ireland owing to its milder climate. It must be remembered that during the height of the glacial epoch Ireland was continental, so that these plants may have followed the retreating ice to their present stations and survived the subsequent depression. This seems more probable than that so many species should have reached Ireland for the first time during the last union with the continent subsequent to the glacial epoch. The Arctic, Alpine, and American plants may all be examples of species which once had a wider range, and which, owing to the more favourable conditions, have continued to exist in Ireland while becoming extinct in the adjacent parts of Britain and Western Europe.

As contrasted with the extreme scarcity of peculiar species among the flowering plants, it is the more interesting and unexpected to find a considerable number of peculiar mosses and Hepaticæ, some of which present us with phenomena of distribution of a very remarkable character. For the following lists and the information as to the distribution of the genera and species I am indebted to Mr. William Mitten, one of the first authorities on these beautiful little plants. That of the mosses has been corrected for this edition by Dr. R. Braithwaite, and several species of hepaticæ have been added by Mr. Mitten.

List of the Species of Mosses and Hepaticæ which are peculiar to the British Isles (or not found in Europe).

(Those belonging to non-European genera in Italics.)

Many of the above are minute or obscure plants, and are closely allied to other European species with which they may have been confounded. We cannot therefore lay any stress on these individually as being absent from the continent of Europe so much of which is imperfectly explored, though it is probable that several of them are really confined to Britain. But there are a few—indicated by italics—which are in a very different category; for they belong to genera which are altogether unknown in any other part of Europe, and their nearest allies are to be found in the tropics or in the southern hemisphere. The four non-European genera of mosses to which we refer all have their maximum of development in the Andes, while the three non-European Hepaticæ appear to have their maximum in the temperate regions of the southern hemisphere. Mr. Mitten has kindly furnished me with the following particulars of the distribution of these genera:—

Bartramidula. Asia, Africa, S. America and Australia, but not Europe or N. America.

Streptopogon is a comparatively small genus, with seven species in the Andes, one in the Himalayas, and three in the south temperate zone, besides our English species.

Daltonia is a large genus of inconspicuous mosses, having seventeen species in the Andes, two in Brazil, two in Mexico, one in the Galapagos, six in India and Ceylon, five in Java, two in Africa, and three in the Antarctic Islands, and one in Ireland.

Hookeria (restricting that term to the species referable to Cyclodictyon) is still a large genus of handsome and remarkable mosses, having twenty-six species in the Andes, eleven in Brazil, eight in the Antilles, one in Mexico, two in the Pacific Islands, one in New Zealand, one in Java, one in India, and five in Africa—besides our British species, which is found also in Madeira and the Azores but in no part of Europe proper.

These last two are very remarkable cases of distribution, since Mr. Mitten assures me that the plants are so markedly different from all other mosses that they would scarcely be overlooked in Europe.

The distribution of the non-European genera of Hepaticæ is as follows:—

Chasmatocolia. South America and Ireland.

Acrobolbus. A small genus found only in New Zealand and the adjacent islands, besides Ireland.

Petalophyllum. A small genus confined to Australia and New Zealand in the southern hemisphere, Algeria, and Ireland in the northern. We have also one of the Hepaticæ—Mastigophora Woodsii—found in Ireland and the Himalayas, but unknown in any part of continental Europe. The genus is most developed in New Zealand.

These are certainly very interesting facts, but they are by no means so exceptional in this group of plants as to throw any doubt upon their accuracy. The Atlantic islands present very similar phenomena in the Rhamphidium purpuratum, whose nearest allies are in the West Indies and South America; and in three species of Sciaromium, whose only allies are in New Zealand, Tasmania, and the Andes of Bogota. An analogous and equally curious fact is the occurrence in the Drontheim mountains in Central Norway, of a little group of four or five peculiar species of mosses of the genus Mnium, which are found nowhere else; although the genus extends over Europe, India, and the southern hemisphere, but always represented by a very few wide-ranging species except in this one mountain group!^[137]

Such facts show us the wonderful delicacy of the balance of conditions which determine the existence of particular species in any locality. The spores of mosses and Hepaticæ are so minute that they must be continually carried through the air to great distances, and we can hardly doubt that, so far as its powers of diffusion are concerned, any species which fruits freely might soon spread itself over the whole world. That they do not do so must depend on peculiarities of habit and constitution, which fit the different species for restricted stations and special climatic conditions; and according as the adaptation is more general, or the degree of specialisation extreme, species will have wide or restricted ranges. Although their fossil remains have been rarely detected, we can hardly doubt that mosses have as high an antiquity as ferns or Lycopods; and coupling this antiquity with their great powers of dispersal we may understand how many of the genera have come to occupy a number of detached areas scattered over the whole earth, but always such as afford the peculiar conditions of climate and soil best suited to them. The repeated changes of temperature and other climatic conditions, which, as we have seen, occurred through all the later geological epochs, combined with those slower changes caused by geographical mutations, must have greatly affected the distribution of such ubiquitous yet delicately organised plants as mosses. Throughout countless ages they must have been in a constant state of comparatively rapid migration, driven to and fro by every physical and organic change, often subject to modification of structure or habit, but always seizing upon every available spot in which they could even temporarily maintain themselves.^[138]

Here then we have a group in which there is no question of the means of dispersal; and where the difficulties that present themselves are not how the species reached the remote localities in which they are now found, but rather why they have not established themselves in many other stations which, so far as we can judge, seem equally suitable to them. Yet it is a curious fact, that the phenomena of distribution actually presented by this group do not essentially differ from those presented by the higher flowering plants which have apparently far less diffusive power, as we shall find when we come to treat of the floras of oceanic islands; and we believe that the explanation of this is, that the life of species, and especially of genera, is often so prolonged as to extend over whole cycles of such terrestrial mutations as we have just referred to; and that thus the majority of plants are afforded means of dispersal which are usually sufficient to carry them into all suitable localities on the globe. Hence it follows that their actual existence in such localities depends mainly upon vigour of constitution and adaptation to conditions just as it does in the case of the lower and more rapidly diffused groups, and only partially on superior facilities for diffusion. This important principle will be used further on to afford a solution of some of the most difficult problems in the distribution of plant life.^[139]