ELMINIUS. Leach. Zoological Journal, vol. 2, July, 1825.
Compartments four: parietes not porose. Basis membranous.
Distribution, Southern temperate seas.
General Appearance.—Shell conical, with a strong tendency in most of the species to become cylindrical: orifice generally large. Walls either thin and smooth, or thick and plicated longitudinally. Colours various, pale purple, greenish, white, and, in E. plicatus, owing to the exposure of an intermediate lamina of shell, bright orange-yellow. Radii, either of considerable width, with their summits oblique and rounded, as in the first two species of the genus, or very narrow, as in the last two species. Elminius plicatus is the largest species, and is sometimes one inch in basal diameter. The outer surface of this latter species is occasionally much corroded.
Scuta: these are of the usual shape; in E. Kingii and modestus there is no adductor ridge and no crests for the depressor muscles; in E. plicatus and simplex, on the other hand, there is a well developed adductor ridge and crests for the lateral depressor muscles; in some individuals, also, of E. plicatus there are small crests for the rostral depressores.
The Terga are remarkable for their variability in all the species; in many specimens of E. Kingii and modestus the basal margin on the carinal side of the spur is deeply hollowed out. The width and acumination of the spur varies in all the species. In E. plicatus and simplex this valve is remarkably like that of Tetraclita porosa. In some specimens of E. Kingii the terga and scuta are firmly calcified together.
Structure of the Parietes and Radii.—As in Tetraclita, the two lateral compartments are necessarily broad. The parietes are never porose, but consist, in appearance, of a single layer of shell. In E. modestus the basal internal edges of the parietes are smooth, but in the other species they are striated longitudinally with short ridges, or sometimes with sub-cylindrical projections. In those specimens of E. plicatus, which have externally suffered much corrosion, the walls have been rendered extremely thick, by the inward production of these ridges or plates; and in this case the ridges are not confined to the basal edges, but extend upwards close to the sheath. The basal surfaces of the walls in these latter specimens resemble those of Chelonobia, but the walls in that genus have an internal lamina, which here is not the case. The radii are wide in E. Kingii, and of moderate width in E. modestus, with their summits oblique and smoothly rounded, and their sutural edges not in the least crenated. In E. simplex they are extremely narrow, smooth-edged, and rounded: in E. plicatus they are narrow, and in this species alone the sutural edge is sinuous, and sends inwards short ridges or teeth. The alæ, in all the species except this last, are likewise smooth-edged. The lower edge of the sheath depends, more or less freely, in all the species, except in E. Kingii.
Basis, membranous in all four species. In E. modestus, the true basal membrane is extremely thin, and is divided into concentric slips: on its inner surface there are attached numerous cement-ducts, varying from 1/3000 to 1/2000 of an inch in diameter, repeatedly trifurcating, rarely forming hexagonal or quadrangular loops, and with the branches placed approximately parallel to each other. Beneath the true basal membrane there is a complicated layer of cement, in the form of a network, or of separate tubes, or in beads and patches. In E. Kingii, the basal membrane presented a wonderfully complicated appearance, in part due to the cement forming a mass of inosculating fibres; many of these fibres seemed to end in circular discs of cement.
Neither the Mouth or Cirri offer any noticeable generic characters, as distinct from Balanus and several other genera. The Branchiæ, in E. plicatus, are well developed and moderately plicated. In E. modestus they are small, not plicated, but with a rounded sinuous margin: in a specimen having a basal diameter of 25/100, the branchiæ in total length were only 4/100 of an inch. At the bottom of the sack I observed some inwardly pointed, tapering filaments, such as occur in Balanus. In this same species I measured the ova, which were unusually elongated, being 19/2000 in length; I may add, that the probosciformed penis was actually thrice the length of the animal’s body in some small but mature specimens (with ova), having a shell with a basal diameter of 16/100 of an inch.
Distribution and Habitats.—This genus is remarkable, inasmuch as it is not distributed over the whole globe: three of the species occur very commonly on the shores of New South Wales, Van Diemen’s Land, and New Zealand; not extending, as far as I can judge, much north of Sydney: the fourth species is confined to South America, ranging from the Falkland Islands and Tierra del Fuego, as far north as Chiloe. Elminius, therefore, appears to be strictly a southern genus. Elminius Kingii and modestus represent each other on the American and Australian continents; so I believe E. plicatus, in New Zealand, represents E. simplex in New South Wales and Van Diemen’s Land. The species are all attached to tidal rocks and shells. E. Kingii is sometimes attached to floating wood. At the Falkland Islands, the last-mentioned species adhered to some rocks, in a running brook of fresh water, at most eighteen inches under high-water mark, so that for the greater part of each tide it was exposed to absolutely fresh water. At Sydney I found E. modestus adhering to oysters in a muddy lagoon, almost separated from the sea, and apparently very unfavorable for cirripedes.
Affinities.—This genus can be distinguished from Tetraclita only by the four compartments not being porose, and by the basis being always membranous; whereas, in Tetraclita purpurascens alone it is membranous. Elminius Kingii and modestus, on the one hand, are closely allied together, as are E. simplex and plicatus on the other hand. The last-named species, in the characters of its opercular valves and in its shell, comes nearest to Tetraclita. In T. rosea we have seen that there is only a single row of parietal tubes, and the outer lamina of the shell is strengthened (as, indeed, it is in most of the other species of the genus, and in Balanus) by small longitudinal plates or ridges, which are similar and homologous to those on the internal basal edges of the parietes in three of the species of Elminius; so that the difference in the structure of the parietes, in Tetraclita and Elminius, is small.
ELMINIUS KINGII. J. E. Gray. Zoological Miscellany, p. 13, 1831.
------ LEACHII. King and Broderip. Zoological Journal, vol. 5, 1832-1834, p. 334, and appendix to King and Fitzroy’s Voyages.
------ ------ G. B. Sowerby. Genera of Recent and Fossil Shells, Plate.
Shell smooth, gray or dirty white: radii broad, smooth-edged: scutum without an adductor ridge; tergum with the spur distinct from the basi-scutal angle: scutum and tergum sometimes calcified together.
Hab.—Tierra del Fuego, Falkland Islands, Chiloe. Attached to tidal rocks and sometimes to floating timber; Mus. Brit., Darwin, &c.
General Appearance.—Shell fragile, either steeply conical with a large orifice, or sub-cylindrical; surface smooth, grayish or white, with large portions covered by pale brown epidermis. Radii broad with their summits oblique, smooth, slightly arched, exhibiting a large surface of the alæ. The alæ usually have their summits much less oblique than those of the radii; the portion added during diametric growth is of a dead white colour. The growth ridges on the scuta are very little prominent, and are crossed by a very obscure band of blueish-gray. The largest specimen which I have seen was .8 in basal diameter, and the longest cylindrical variety .55 of an inch in height.
The Scuta are remarkable for not having any adductor ridge or crests for the depressor muscles; the articular ridge is prominent, but it is short, not extending down half the valve. I have mentioned under the genus, that in many specimens at the Falkland Islands the scuta and terga were calcified together.
The Terga are rather small: the basal margin on the carinal side of the spur is always hollowed out, but to a very variable degree, as may be seen in the three figures (6 c-6 e); this margin is generally dentated with one or two little points; and an inner lamina of shell sometimes depends beneath the outer lamina, to which the opercular membrane is attached, as may be seen in the figure (6 d) of the external surface of the valve. The crests for the depressor muscles are well developed. The tergal margin is broadly inflected, and the articular ridge prominent, making the articular furrow deep. The spur is rather narrow, and is either (6 d, 6 e) bluntly or sharply pointed. The basal margin on the scutal side of the spur, is hollowed out, but to a variable depth.
Structure of the Parietes and Radii.—The parietes are thin; at their internal basal edges they are finely striated in longitudinal lines. The radii are solid, with quite smooth edges; they are generally covered by the epidermis. The sutural edges of the alæ are likewise smooth, these are added to largely during the diametric growth; and their summits, as already stated, are much less oblique than the summits of the radii. The internal surface of the shell is smooth, and is tinted pale dull purple. The lower edge of the sheath can hardly be said to be free. The carinal margins of the compartments project a little inwards.
Mouth: the labrum is deeply notched, and supports five little teeth on each side; the palpi are thickly clothed with spines on their inner sides; the mandibles have five or only four teeth: the maxillæ are notched, and the outer maxillæ bilobed.
Cirri: the first pair has one ramus nearly twice as long as the other. The three posterior cirri are elongated, and each segment supports five or six pairs of long spines, with a few minute intermediate bristles.
Shell folded longitudinally, greenish or white: radii of moderate breadth, smooth edged: scutum without an adductor ridge: tergum narrow, with the spur confluent with the basi-scutal angle.
Hab.—New South Wales; Van Diemen’s Land; New Zealand; very commonly attached to littoral shells and rocks; associated with Balanus trigonus and vestitus; Mus. Brit., Cuming, Stutchbury, Darwin.
General Appearance.—Shell conical, generally rather steep, occasionally depressed: walls longitudinally folded, sometimes very deeply, sometimes only to a slight degree: colour dull greenish or white. Radii of moderate width, with their summits very oblique, smooth and slightly arched: alæ much exposed, with their summits less oblique than those of the radii: the portion added to the alæ during the diametric growth differs much in appearance from the other portion. The scuta have the growth ridges but little prominent; they are crossed by a faint longitudinal band of gray. The largest specimen out of the many which I have seen, was under .4 of an inch in basal diameter.
Scuta, destitute of an adductor ridge and of crests for the depressor muscles: the articular ridge is moderate; but the articular furrow is rather wide: the internal occludent margin is much thickened. The Terga are narrow and small; they are somewhat variable in shape, caused by the degree to which the basal margin is hollowed out (fig. 1 c-1 e), and likewise by the extent to which the upper end of the valve has been worn away. No spur is apparent, for it is confluent with the basi-scutal angle of the valve. The articular ridge is very prominent, and runs down to the basi-scutal angle; and as the valve in this part is extremely narrow, with the spur not developed, it here assumes a channelled structure. The basi-carinal corner of the valve is furnished with rather feeble crests for the depressor muscles, and in those varieties in which the basal margin is much hollowed out, this part is remarkably narrow.
Structure of the Parietes and Radii.—The internal basal edges of the parietes and the sutural edges of the radii and alæ, are all smooth. The lower edge of the sheath depends freely. In the green varieties the colour is most distinct on the internal surface of the shell. The four compartments separate very easily when the shell has been ill preserved in spirits, or after a very short immersion in caustic potash.
Mouth, as in E. Kingii, excepting that there are only three teeth on each side of the notch (which is deeper) on the labrum. The cirri resemble those of E. Kingii; the segments in the sixth pair are equally elongated, and bear five or six pairs of spines.
Affinities.—This species is closely allied to its South American representative E. Kingii; the differences consist in its smaller size, often greenish colour, more folded walls, and narrower radii: the internal basal edges, also, of the parietes are here smooth, instead of being striated, as in E. Kingii. The terga present even more obvious differences, in their narrowness, channelled under surface, and in the absence of the spur, or more properly in its confluence with the basi-scutal angle of the valve.
ELMINIUS PLICATUS. J. E. Gray. Appendix to Dieffenbach’s Travels in New Zealand, p. 269, 1843.
Shell deeply folded longitudinally, corroded, coloured in parts orange: radii very narrow, with their edges sinuous, and slightly dentated: scutum having an adductor ridge.
Hab.—New Zealand; New South Wales(?). Attached to rocks, often coated by Chamæsipho columna; Mus. Brit. and Cuming.
General Appearance.—Shell tubulo-conical, or conical, rarely depressed; strong, rugged, coloured in parts bright orange; deeply plicated longitudinally, but with the upper parts corroded and smooth. Orifice large. The sutures are indistinct and almost obliterated; the radii, when most developed, are narrow. Some specimens have their whole surface deeply corroded; in which case they are finely striated longitudinally, or pitted, and are of a gray or brown colour. The largest specimens are one inch in basal diameter, but one depressed specimen was 1.3 in diameter; another was rather under one inch in diameter, and one inch in height.
Scuta; beginning with the common tubulo-conical and not much corroded specimens, the valve (fig. 2 c) is moderately elongated, but in a rather variable degree. A prominent adductor ridge runs, from a little above a middle point of the basal margin, along the slightly prominent articular ridge: the articular furrow is moderately wide. There are distinct crests for the lateral depressores. In the conical, corroded specimens, the scuta (fig. 2 e) are considerably broader, with the articular ridge much more prominent, and the furrow wider: in one such specimen, there were crests for the rostral depressor muscle.
The Terga, in the commoner variety, resemble those of Tetraclita porosa; the spur adjoins the basi-scutal angle of the valve: the articular ridge is moderately prominent, and the furrow moderately deep. The valve is beaked, with an unusually large internal tube for the thread of corium: the beak, however, is often worn away. In the depressed much corroded specimens, the terga (fig. 2 f), like the scuta, are broader and shorter than in the commoner variety; and the spur more especially is broader. The scutal margin is much more widely inflected, and the articular ridge much more prominent; consequently the articular furrow is much deeper.
Structure of the parietes and radii.—The orange or yolk-of-egg colour, which is so conspicuous a character in the present species, is due to a layer of shell between the inner and outer lamina, and is exposed only by the corrosion of the latter. Hence the very base of the shell is not of this colour; nor are the uppermost and still more deeply corroded portions, for here the orange-coloured layer has been removed. The sheath is orange-coloured, and the operculum, to a certain extent, is similarly tinted. The epidermis on the parietes, where preserved quite close to the basis, supports remarkably strong spines, about 1/100th of an inch in length. The basal internal edges of the walls are rather coarsely striated with irregular short ridges and sub-cylindrical points; and the walls in most of the specimens are regularly and deeply folded, which, with the little ridges, gives the appearance represented in fig. 2 b, Pl. 12. I have stated, under the Genus, that in the corroded and depressed specimens, the walls are rendered extremely thick by the inward production and upward extension of these same ridges and points; the under surface of the shell acquiring almost the appearance of Chelonobia caretta. The Radii are often not developed, even the sutures being obscure; when most developed, they are narrow, with the outer lamina along the growing edge sinuous, giving to the sutures a crenated appearance. The sinuosities on the growing edge generally send inwards short ridges or septa, like those on the sutural edges of the radii in most Balanidæ, but of which there is no trace in the other species of Elminius. In very minute, colourless specimens, about the 1/20th of an inch in diameter, the radii are quite smooth-edged. The alæ have their edges strongly crenated. The lower edge of the sheath depends freely.
Mouth: the labrum shows some tendency to be bullate; the notch is broad and shallow: the palpi have a thick brush of bristles on their inner sides. The mandibles have four or five teeth. In the maxillæ, the upper spines above the broad notch, are very strong. In the outer maxillæ, the two lobes are widely separated.
Cirri: in the first pair, one ramus is about one fifth longer than the other. In the third pair, the posterior ramus is one fourth longer than the anterior ramus, and its terminal segments are tapering, each having a single circle of bristles: the other segments, and those of the shorter ramus, support many coarsely pectinated spines. In the sixth cirrus, the segments are protuberant in front, and carry four pairs of stout spines, with a tuft of fine bristles between them.
Affinities.—This species differs considerably from the first two of the genus. In several characters it approaches nearer than the other species to Tetraclita, especially to T. porosa;—namely, in the scutum having an adductor ridge and crests for the lateral depressores, in the whole form of the tergum, in the thick walls liable to much corrosion, in the narrow radii, and in their edges, as well as those of the alæ, being crenated; and, lastly, in the character of the cirri, more especially of the third pair, with its coarsely pectinated spines. It also approaches, in all its characters, Balanus imperator and flosculus.
Shell ribbed longitudinally, dirty white; radii extremely narrow, smooth-edged; scutum having an adductor ridge.
Hab.—New South Wales (Sydney and Twofold Bay); Van Diemen’s Land; tidal rocks, often attached to other Cirripedes, and associated with Balanus nigrescens, Tetraclita purpurascens, Catophragmus polymerus; Mus. Brit., Cuming, Stutchbury, and Darwin.
This species, of which I have seen specimens from the above three localities, all exactly agreeing with each other, is perhaps the Australian representative of E. plicatus, which seems to be confined to New Zealand.[113] In all essential points it comes so near that species, that I shall make the greater part of my description comparative.
[113] I am bound to state that I have seen two specimens of E. plicatus marked Sydney, and one marked Moreton Bay, but in both cases the collectors had visited New Zealand, so that a wrong habitat by mistake might easily have got attached to the specimens in question.
General Appearance.—In external appearance there is considerable difference from E. plicatus, for E. simplex is generally of a regular conical shape, of a dirty-white colour, with the surface well preserved, having moderately wide, not very prominent longitudinal ribs. The orifice is rather small and pentagonal. The radii are extremely narrow or linear, with quite smooth edges; the sutures, however, are always very distinct, and in the upper part, the alæ are generally rather widely exposed, as viewed from the outside. The largest specimen which I have seen was .7 of an inch in basal diameter.
The opercular valves are closely similar to those of E. plicatus, but the scutum is generally a little more elongated, and the articular furrow not so deep: in accordance with this last fact, the articular ridge in the tergum is not so prominent as in E. plicatus; but we have seen that these several characters are highly variable in E. plicatus. The slope of the basal margin of the tergum towards the spur varies in the present species, in a strictly analogous manner, as it does in Tetraclita porosa.
Structure of the Parietes and Radii.—The parietes are not so thick as in E. plicatus; internally they are tinted pale purple; when broken transversely, a row of microscopically minute orange-coloured dots can generally be distinguished between the outer and inner laminæ; and these evidently represent the orange-coloured layer in E. plicatus. The sheath also exhibits a faint tinge of orange. The radii are very narrow, and are quite smooth-edged, differently from in E. plicatus. The edges of the alæ barely exhibit a trace of being crenated.
In the body I could perceive no difference from E. plicatus, excepting that in the third pair of cirri the two rami are like each other, and do not support any coarsely pectinated, only serrated, spines; but after what we have seen on the variability of these very same characters in Tetraclita porosa, I dare not trust to them. The three posterior pairs of cirri, also, seem here to be more elongated in proportion to the others, than in E. plicatus.
Affinities.—It is certain that this species is most closely allied to E. plicatus; but as I have seen many specimens of the latter brought by different persons from New Zealand, and as I have observed in them no approach to the characters of E. simplex, which, in specimens from three localities, also appear to be constant, I have considered the two forms as specifically distinct. The present species differs from E. plicatus, in its white, conical, moderately ribbed, well preserved, smaller shell; and more especially in the orange-coloured intermediate lamina of E. plicatus being here represented only by microscopically minute dots. But the radii being smooth-edged, is the most important differential character, though in E. plicatus, during its earliest growth, whilst still immature and colourless, the radii are likewise smooth-edged.