MALACOTTA BIVALVIS. _Schumacher._ Essai d"un Nouveau Syst., &c., 1817.
GYMNOLEPAS CUVIERII. _De Blainville._ Dict. des Sc. Nat., Art.
Mollusc., Plate, fig. 1, 1824.
[37] Many authors (Poli, Montagu, &c.,) have doubted from the strangely mistaken description, viz., "ore octovalvi dentato,"
whether this species could be the _Lepas aurita_ of Linnaeus. But in the Linnean Society, there is a proof plate from Ellis"s "Account of several rare Species of Barnacles," in "Phil.
Trans.," 1758, with an excellent figure of the _C. aurita_, and on the margin in Linnaeus"s handwriting is the name _Lepas aurita_.
_C. capitulo duobus tubularibus quasi-auribus instructo, pone terga rudimentalia (saepe nulla) positis: scutis bilobatis: carina nulla, aut omnino rudimentali: pedunculo longo, a capitulo distincte separato._
Capitulum with two tubular ear-like appendages, seated behind the rudimentary and often absent terga; scuta bilobed; carina absent, or quite rudimentary; peduncle long, distinctly separated from the capitulum.
Filaments attached to the pedicels of the second cirrus; two upper spines of the maxillae pectinated.
_Hab._--Mundane; extremely common. On ships" bottoms from all parts of the world. Arctic Sea. Greenland. Pacific Ocean. Often attached to Coronulae on Whales. On slow-moving fish, according to Dr. A. Gould. Often a.s.sociated with _C. virgata_, and _Lepas anatifera_, _L. Hillii_, and _L. anserifera_.
_General Appearance._--The capitulum (seen from above in Pl. III, fig. 4 _a_) is slightly compressed, almost globular, composed of thick membrane, with two large, ear-like, flexible, tubular, folded appendages, at the upper end, opening into the sack. These appendages are seated behind the rudimentary terga when such are present, or behind the spots which they would have held if not aborted. In a young condition they are tubular, but not folded; and often, according to Prof. Macgillivray, either one or both are at first imperforate. They are formed externally of the outer membrane of the capitulum (rendered thin where folded), and internally of a prolongation of the inner tunic of the sack; between the two, there is, as around the whole sack, a double layer of corium. A section across both appendages, near their bases, is given in Pl. III, fig. 4 _b_, showing how they are folded,--the chief fold being directed from below upwards, with a smaller fold, not always present, from between the two, outwards. The folds sometimes do not exactly correspond on opposite sides of the same individual; they are almost confined to the lower part, the orifice itself being often simply tubular. These appendages are sometimes very nearly as long as the whole capitulum: a section near their bases is sub-triangular. I shall presently make some remarks on their functions and manner of formation.
The _Scuta_, as well as the other valves, are imperfectly calcified: shape, variable. They usually consist of two lobes or plates, placed at above a right angle to each other, and rarely (fig. 4 _c_) almost in a straight line; the lower lobe is more pointed and narrower than the upper; the two correspond to the lower and middle lobes in the scuta of _C. virgata_, the upper one being here absent.
The _Terga_ are developed in an extremely variable degree; they are often entirely cast off and absent. In very young specimens, they are of the same length with the carina, but after the carina has ceased to grow, the terga always increase a little, and sometimes to such a degree as to be even thirty or forty times as long as carina. When most developed (fig. 4 _a_) they are not above one third as long as the scuta, to which they lie at nearly right angles; they consist of imperfectly calcified plates, square at both ends, slightly broader and thinner at the end towards the carina, where they are a little curled inwards, than at the opposite end; they are not quite flat in any one plane; internally they are slightly concave; finally, I may add, they nearly resemble in miniature the terga of _C. virgata_. In full grown specimens, the terga almost invariably drop out and are lost; but even in this case, a long brownish cleft in the membrane of the capitulum, marks their former position. The orifice of the capitulum is usually notched between the terga, or between the clefts left by them; on each side of the notch there is a slight prominence. In some few cases, however, there is no trace of this notch. Behind the terga or the clefts, the great ear-like appendages, as we have seen, are situated.
_Carina_, rudimentary (fig. 4) and often absent; it is pointed-elliptical, and is rarely above the 1/40th of an inch long.
After arriving at this full size, calcareous matter is added to the under surface over a less and less area, so that it becomes internally pointed, and finally, in place of calcareous matter, continuous sheets of chitine are spread out beneath it; hence, during the disintegration of the outer surface, the carina comes to project more and more, and at last drops out; subsequently, even the little hole in which it was imbedded, disintegrates and disappears.
_Peduncle_, cylindrical, distinctly separated from the capitulum, and generally twice or thrice as long as it: the thickness of the outer membrane generally great, but variable: surface of attachment variable, either pointed, or widely expanded, or formed into divergent projections.
_Filamentary Appendages_, seven on each side, highly developed, long and tapering; there are two beneath the basal articulation of the first cirrus, and one on the posterior margin of the pedicel of each cirrus, excepting the sixth pair; the filaments on the pedicels are nearly twice as long as the cirri themselves.
_Mouth_,--mandibles, with the five teeth nearly equidistant, and towards their bases finely pectinated on both sides; inferior angle rudimentary, often represented by a single minute spine: in one specimen, there were only four teeth on one side. Maxillae, with five steps, not very distinct from each other, with the first step much curved. The larger of the two upper great unequal spines is pectinated, like the teeth of the mandibles; there is a third long finer spine beneath the upper large pair.
_Cirri_ rather short, broad, with the anterior faces of the segments protuberant, especially those of the first cirrus and of the anterior ramus of the second pair: spines on the anterior cirri doubly serrated.
Posterior cirri, with the intermediate spines between the pairs, long; dorsal tufts, minute. On the lower segment of the pedicels of the four posterior cirri, there are two separate tufts of bristles.
_Colours_ extremely variable; sometimes five longitudinal bands of dark purple can be distinctly seen (as in _C. virgata_) on the peduncle, these bands becoming more or less confluent on the capitulum; at other times, the capitulum is more or less spotted, or often nearly uniformly purple: the sack, cirri and trophi are, also, purple.
_Size._--The largest specimen which I have seen was, including the peduncle and ears, five inches in length, the capitulum itself being rather above one inch in length, and 7/10ths of an inch in breadth.
_General Remarks._--I have come to the same conclusion with Prof.
Macgillivray, concerning the variability of this form, and I believe there is only one true species. With respect to Dr. Coates"s species, viz., _Otion depressa_ and _O. saccutifera_, though I have not seen specimens, I can hardly doubt, from the insufficient characters given, that they are mere varieties.
With respect to the ear-like appendages, we shall presently see in _C.
virgata_, that at corresponding points on the capitulum (Tab. III, fig.
2 _b_), there are two slight, closed prominences. According to Professor Macgillivray, in _C. aurita_, every gradation can be followed by which the appendages, at first closed, become tubular and open. The opening would ensue, if the corium became absorbed at the bottom of the appendages whilst still imperforate, for then the inner tunic would be cast off at the next moult and would not be re-formed, whilst the outer membrane would gradually disintegrate together with the other external parts of the capitulum, and not being re-formed at this point, an aperture would at last be left. These appendages have no relation to the generative system: the ovarian tubes, which surround the sack do not extend into them; nor do the ovigerous lamellae. I believe, that their function is respiratory: the corium lining them is traversed by river-like circulatory channels, and their much-folded, tubular and open structure must freely expose a large surface to the circ.u.mambient water.
Why this species should require larger respiratory organs than any other, I know not. In this species, moreover, the filamentary appendages are developed to a greater extent than in any other cirripede; in most genera, the surface of the body and of the sack suffices for respiration.
2. CONCHODERMA VIRGATA. Pl. III, fig. 2. Pl. IX, fig. 4.
LEPAS VIRGATA. _Spengler._ Skrifter Naturhist. Selbskabet., B. i, 1790, Tab. vi, fig. 9.
---- CORIACEA. _Poli._ Test. utriusque Sicil., Pl. vi, fig. 20, 1795.
---- MEMBRANACEA. _Montagu._ Test. Brit. Supp., p. 164, 1808, et Linn. Trans., vol. xi, Tab. xii, fig. 2.
CONCHODERMA VIRGATUM. _Olfers._ Magaz. Gesells. Naturfor. Freunde, Berlin, 1814, p. 177, (3d Quartel).[38]
BRANTA VIRGATA. _Oken._ Lehrbuch der Gesell., Th. ii, p. 362, 1815.
SENOc.l.i.tA FASCIATA. _Schumacher._ Essai d"un Nouveau Syst., 1817.
CINERAS VITTATA. _Leach._ Encyclop. Brit. Supp., Tom. iii, Plate.
1824.
---- CRANCHII (!) CHELONOPHILUS (!) OLFERSII (!). _Leach._ Tuckey"s Congo Expedition, p. 412, 1818.
---- MEGALEPIS (!) MONTAGUI (!) RISSOa.n.u.s. _Leach._ Zool. Journal, vol. ii, p. 208, 1825.
---- MEMBRANACEA. _Macgillivray._ Edin. New Phil. Journal, vol.
x.x.xix, p. 171, 1845.
---- BICOLOR. _Risso._ Hist. Nat. des Productions, &c., 1826, Tom.
iv, p. 383.
---- VITTATUS. _Brown._ Ill.u.s.t. of Conch., 1844, Pl. li, figs.
16-18.
GYMNOLEPAS CRANCHII. _De Blainville._ Dict. des Sci. Nat. Hist., 1824.
PAMINA TRILINEATA (!) (Var. Monstr.). _J. E. Gray._ Annals of Phil., vol. x, 1825.
[38] See page 136 respecting this date.
_C. Scutis trilobatis: tergis intus concavis, apicibus introrsum leviter curvatis: carina modica, leviter curvata: pedunculo in capitulum coalescente._
Scuta three-lobed: terga concave internally, with their apices slightly curved inwards: carina moderately developed, slightly curved: peduncle blending into the capitulum.
No filament attached to the pedicel of the second cirrus.
_Var. chelonophilus_ (Pl. III, fig. 2 _c_). Terga, minute, nearly straight, solid, ac.u.minated at both ends, placed far distant from the other valves: carina, either minute and ac.u.minated at both ends, or moderately developed and slightly arched and blunt at both ends: lateral lobes of the scuta broad: valves imperfectly calcified.
_Hab._--Mundane: extremely common on ships" bottoms from all parts of the world. Falkland Islands. Galapagos Islands, Pacific Ocean. Attached to sea-weed, turtle and other objects. Often a.s.sociated with _Conchoderma aurita_, _Lepas anatifera_, _L.
Hillii_, and _L. anserifera_.
_General Appearance._ Capitulum, flattened, gradually blending into the peduncle; summit square, rarely obtusely pointed. Membrane, thin.
Valves, thin, small, sometimes imperfectly calcified, very variable in shape and in proportional length, and therefore, situated at variable distances from each other, but always remote and imbedded in membrane.
_Scuta_, trilobed, consisting of an upper and lower lobe (the latter generally the broadest), united into a straight flat disc, with a third lobe standing out from the middle of the exterior margin, generally at an angle of from 50 to 70 (rarely at right angles) to the upper part, and generally (but not always) bending a little inwards. The shape of the lateral lobe varies from rounded oblong to an equilateral triangle; as it approaches this latter form, it becomes much wider than the upper or lower lobes. In one specimen, and only on one side, the scutum (fig.
2 _d_) presented five points or projections. In some specimens, the scuta are very imperfectly calcified, and consist of several quite separate beads of calcareous matter of irregular shape, held together by tough brown membrane.