[346] The only exception appears to be Pedipes, while in Cassidula and Scarabus the absorption is partial (Crosse and Fischer, Journ. de Conch. xxx. p. 177 f.).

[347] Strombus and Pteroceras (see Fig. 99, p. 200) exceptionally develop a siphonal notch which is distinct from the anterior canal.

[348] The columella, as distinct from the columella lip, is the solid pillar of shell round which the whorls are coiled (Fig. 177), the lower, or anterior portion of which alone is usually visible.

[349] J. E. Gray, Phil. Trans. 1833, p. 812.

[350] W. H. Dall, Amer. Journ. Sc. xxxviii. p. 445 f.

[351] The term epidermis, as distinct from periostracum, is properly restricted to the outer layer of the skin of the mantle and body generally.

[352] J. Lewis, Proc. Bost. Soc. vi. p. 149.

[353] Journ. of Conch. v. p. 66.

[354] The Dispersal of Shells, pp. 182–195.

[355] E. A. Smith, P. Z. S. 1892, p. 259.

[356] C. T. Musson, Proc. Linn. Soc. N. S. Wales (2), v. p. 883.

[357] Scient. Results Sec. Yarkand Exped. “Mollusca,” pp. 1–16.

[358] Mr. H. W. Kew, The Dispersal of Shells, has brought together a very large series.

[359] The Naturalist in Nicaragua, p. 334 f.

[360] Morelet, Journal de Conch. 1875, p. 194.

[361] Pollonera, Boll. Mus. Zool. Torino, v. 1890, No. 87.

[362] South and south-western France, however, belong to the Mediterranean Sub-region.

[363] The coast-line of north-east China, including Corea and Japan to north Niphon, is much more definitely tropical than the adjacent inland districts. The coast-line, therefore, must be placed in the Oriental Region, while the inland districts belong to the Palaearctic Region.

[364] Biol. Centralbl. ii. p. 208.

[365] Craven, Journ. de Conchyl. (3) xxviii. p. 101.

[366] Jahrb. Deutsch. Malak. Gesell. viii. p. 278.

[367] Netchayeff, Kazan Soc. Nat. xvii. fasc. 5.

[368] Fauna der Congerien-Schichten, p. 142.

[369] Streptaxis is a remarkable instance of a mainland genus. Although abundant in the Oriental, Ethiopian, and Neotropical regions, it never seems to occur on any of the adjacent islands, except in the case of Trinidad (1 sp.), which is practically mainland. Omphalotropis, on the other hand, is the exact reverse of Streptaxis in this respect, occurring all over Polynesia and the Malay Is., as far west as Borneo, as well as on the Mascarenes, but never, save in a doubtful case from China, on the mainland of Asia, Australia, or Africa.

[370] The Amboyna group has been much the better explored. Common to both groups are one sp. each of Kaliella, Trochomorpha, Opeas, Leptopoma, Cyclotus, Helicina.

[371] A. H. Cooke, P. Z. S. 1892, pp. 447–469.

[372] Mysol, with 2 Chloritis, 1 Insularia, 1 Cristigibba, is decidedly Papuan.

[373] See especially C. Hedley, Note on the Relation of the Land Mollusca of Tasmania and New Zealand, Ann. Mag. Nat. Hist. (6) xiii. p. 442.

[374] Hedley and Suter, Proc. Linn. Soc. N. S. Wales (2), vii. p. 613. Twenty-one species are “introduced.”

[375] Nine species have been introduced: 6 from Europe, 2 from the West Indies, 1 from the Western Isles.

[376] It is by no means implied that unbroken land communication between India and Madagascar, across the Indian Ocean, ever existed. A series of great islands, whose remains are attested by the Chagos and other banks, would be quite sufficient to account for the results, as we find them. See especially Medlicott and Blanford, Geology of India, vol. i. p. lxviii.

[377] Journ. Cinc. Soc. Nat. Hist. iii. p. 317. The number is doubtless susceptible of very considerable reduction, say by one-half at least.

[378] Simpson, Amer. Nat. xxvii. 1893, p. 354.

[379] Compare von Martens, Malak. Blätt. 1868, p. 169; von Ihering, Nachr. Deutsch. Malak. Gesell. 1891, p. 93.

[380] The distribution of some Pteropoda has been worked out by Munthe, Bih. Svensk. Ak. Handl. XII. iv. 2, by Pelseneer “Challenger” Rep., Zool. xxiii., and by Boas, Spolia Atlantica.

[381] Bull. Mus. C. Z. Harv. xiv. p. 202; xxiii. p. 34 f.

[382] See papers in P. Z. S. 1878–85.

[383] A break in this uniformity may be found underneath the course of a great oceanic current like the Gulf Stream, which rains upon the bottom a large amount of food. A. Agassiz (Bull. Mus. C. Z. Harv. xxi. p. 185 f.) explains in this way the richness of the fauna of the Gulf of Mexico as compared with that of the west coast of tropical America.

[384] On the western coasts of Europe and America, where the change in surface temperature is very gradual, Purpura lapillus (the west American ‘species’ are at best only derivatives) is able to creep as far south as lat. 32° (Mogador) in the former case, and lat. 24° (Margarita Bay) in the latter, the mean annual temperature of the surface water being 66° off Mogador, with an extreme range of only 8°, and that of Margarita Bay 73°, with an extreme range of only 5°. On the eastern coasts, where the Pacific and Atlantic gulf-streams cause a sudden change of temperature, the Purpura is barred back at points many degrees farther north, viz. at lat. 41° (Hakodadi), surface temperature 52°, extreme range 25°; and at lat. 42° (Newhaven), surface temperature 52°, extreme range 30°.

[385] E. A. Smith, P. Z. S. 1890, pp. 247, 317.

[386] A. H. Cook, Ann. Mag. Nat. Hist. (5) xviii. (1886) p. 380 f; E. A. Smith, P. Z. S. 1891, p. 391 f.

[387] C. Keller, Neue denksch. Schw. Gesell. xxviii. 1883, pt. 3.

[388] According to Tate (Trans. Roy. Soc. S. Austr. 1887–88, p. 70), ‘Australian’ species predominate at Freemantle (32°), but Tenison-Woods (J. Roy. Soc. N. S. Wales, xxii. p. 106) holds that the tropical fauna extends as far south as Cape Leeuwin (34°), and that the Australian forms are not predominant until the extreme south. Tenison-Woods regards Cape Byron (31°) as the limit of the tropical fauna on the east coast, while some characteristic tropical genera reach Port Jackson, and a few (e.g. Cypraea annulus) Tasmania.

[389] A full account of the distribution of Voluta is given by Crosse, Journ. de Conchyl. (3) xix. p. 263.

[390] Usually known as ‘Patagonian,’ but since the Magellanic Sub-region includes a considerable part of Patagonia, and since the greater part of sub-region (6) lies out of Patagonia, it has been thought advisable to change the name.

[391] Amer. Nat. xx. p. 931.

[392] W. H. Dall, Proc. Biol. Soc. Washington, v. p. 1 f.

[393] Trans. Connect. Acad. v. p. 177; Zoologist, 1875, p. 4502.

[394] Rep. Scotch Fish. iii. 1885, App. F, p. 67.

[395] Nautilus, vi. 1892, p. 82.

[396] Journ. Mar. Zool. i. pp. 3, 9.

[397] Rep. Brit. Assoc. 1844, Transactions, p. 74; P. Z. S. 1839, p. 35.

[398] It is convenient, but not morphologically correct, to apply the terms ‘ventral’ and ‘dorsal’ in this sense.

[399] φραγμός, partition; σήπιον, cuttle-bone; χόνδρος, long cartilage.

[400] μυέω, close the eyes; ὕψις, sight; contrasted with Oigopsidae (οἰγω, open).

[401] The classification is that of Foord, Catal. Fossil Cephal. Brit. Mus., 1888.

[402] Saville Kent, Proc. Roy. Soc. Queensland, vi. p. 229.

[403] J. Power, Ann. Mag. N. H. (2) xx. p. 334; P. Z. S. 1836, p. 113; Arch. Zool. Exp. Gén. (3) i. 1893, p. 105.

[404] In deference to Bergh’s high authority, the position of a sub-order is here given to the Ascoglossa. It may be doubted whether that position will stand the test of further investigation, and whether the families concerned will not be added to the Cladohepatic Nudibranchs.

[405] This family has also been classified with the Bulloidea and with the Aplysioidea.

[406] It appears more convenient to treat the whole group together, rather than deal with the two sections separately.

[407] An operculum is said to exist in the young forms of Auricula and Parmacella.

[408] Proc. Ac. Philad. 1892, p. 390.

[409] Compare Jackson, Amer. Nat. xxv. p. 11 f.

[410] “A Monograph of the British Fossil Brachiopoda,” Palaeontographical Society, London, vols. i.-v. 1851–84.

[411] Ibid. vol. vi. 1886.

[412] “Contributions to the Anatomy of the Brachiopoda,” Proc. Roy. Soc., vol. vii.

[413] “Untersuchungen über den anatomischen u. histologischen Bau der Brachiopoda Testicardinia,” Jenaische Zeitschrift, vol. xvi., 1883.

[414] “On a living Spinose Rhynchonella from Japan,” Ann. Mag. Nat. Hist., 5th ser., vol. xvii., 1886

[415] Loc. cit. p. 465.

[416] Shipley, “On the Structure and Development of Argiope,” Mitt. aus d. Zool. Stat. zu Neap. Bd. iv. 1883.

[417] Schulgin, “Argiope Kowalevskii,” Zeit. f. wiss. Zool. Bd. 41, 1885.

[418] American Jour. of Sci. and Arts, 3rd series, vol. xvii. 1879.

[419] Loc. cit. p. 470.

[420] “Recherches sur l’Anat. des Brachiopodes Inarticules,” Arch. Zool. Exp. (2), Tome iv., 1886.

[421] “Untersuchungen über den Bau der Brachiopoden,” Jena, 1892.

[422] “Vorläufige Mittheilungen über Brachiopoden,” Zool. Anz. Bd. viii. 1885.

[423] Hancock’s nomenclature is here used. The corresponding names used by King and Brooks are placed in brackets. Their nomenclature is used by many palaeontologists, and is adopted in Fig. 322.

[424] Development of the Brachiopoda, 1873 (Russian).

[425] “Histoire de la Thécidie,” Ann. d. Sci. Nat., Sér. 4, vol. xv., 1861.

[426] “On the Early Stages of Terebratulina septentrionalis,” Mem. Boston Soc. Nat. Hist., vol. ii., 1869. “On the Development of Terebratulina,” Ibid. vol. iii., 1873.

[427] “Choses de Nouméa,” Arch. d. Zool. exp. et gen., 2nd ser., vol. ix., 1891.

[428] J. Barrande, Syst. Silur. Bohème, vol. v., 1879. Hall and Clarke, Introd. Palaeozoic. Brach. (Palaeont. of New York, 1892–1894). Davidson, Monogr. Brit. Foss. Brach. (Palaeont. Soc., 1851–1884). Waagen, Salt Range Fossils (Mem. Geol. Surv. India, 1879–1885).

[429] The results of the investigations of King (Ann. Mag. Nat. Hist., 4th ser., vol. xii., 1873) and of Brooks (Chesapeake Zool. Laboratory, Scientific Results, p. 35, 1879), and the simple nomenclature of these authors are here followed in preference to those of others, owing to the difference of opinion amongst anatomists of the functions and homologies of the muscles. The lateral muscles enable the valves to move backwards and forwards on each other; the centrals close the shell; the umbonals open it; and the transmedians allow a sliding sideways movement of one valve across the other (see also p. 477).

[430] Davidson and King, Quart. Jour. Geol. Soc., xxx. (1874), p. 124.

[431] Amer. Jour. Science, 1890–1893.