OCR Text |
Show 1880.] FERUSSACIA GRONOVIANA. 663 for so thin and fragile a form, possesses considerable powers of vitality, as a large number of them packed together in a corked tube had survived for many weeks. It may be that, being carnivorous, they had been living on their less fortunate companions. The animal (Pl. LXIV. fig. 1) is of a fine bright sea-green colour : the eye-tentacles are dark and thick at their bases, which are contiguous ; the oral very short and blunt; muzzle retractile, and can be produced considerably. It is of darker tint at the extremity of the foot, which has a distinct mucous gland with a truncate lobe above it. There is a well-marked pedal line parallel to the edge of the foot, from which a series of regular transverse furrows extends to the dorsal side ; but the intervals between these furrows are smooth, not papillate : this is seen to extend to the muzzle ; but from the oral tentacles the whole upper part of the neck is strongly and longitudinally grooved. The animal when fully extended is long and narrow, end of foot equal with apex of shell when moving; and the mantle is all round slightly reflected over the thin margin of the peristome. The right dorsal lobe is small, the left is larger (fig. 2). The odontophore (figs. 8, 8 a) consists of over a hundred rows of teeth, about 60 in each row, with a very considerable difference in the size of the centrals and laterals, the centre being very small, bluntly tricuspid, on an elongate oblate base* the next seven having a long pointed central tooth with the two smaller on either side ; tbe outer laterals are minutely evenly tricuspid on broad, oblong, rectangular bases. The dental formula is 2 2 - 7 - 1 - 7 - 2 2 . The jaw (figs. 4, 4 a, 4 b) is peculiar, not hard and chitinous as is usually the case, but thin and elastic, consisting of a thin membranous ribbon, closely ribbed or rather folded longitudinally, and presenting on the anterior side a zigzag or serrated edge. This elastic plicate structure of the jaw is thus quite in accord and adapted most admirably to the retractile muzzle of the animal. The buccal mass is well developed, of rounded form ; the salivary ducts short, the glands of unequal size. Generative organs.-The penis (fig. 7) is short, fusiform, conical near the junction of the vas deferens ; the retractor muscle is given off close to this. The spermotheca is elongately pear-shaped. No dart-sac was observed in the three specimens examined. The ovo-testes (fig. 5) in one specimen appeared to be a mass of globosely pear-shaped follicles united at their basal ends into a duct; but in two specimens (fig. 6) there was found near the apex, embedded in the livers, a dark triangular-shaped organ, which, when examined more closely, was trilobed, uniting in a single duct, streaked and coloured black along its straight terminal margin, and may possibly have consisted of closely packed bundles of spermatozoa. The hermaphrodite duct was not made out, nor the albumen-gland; and I most unaccountably did not notice the exact position, with respect to the right eye-tentacle, of the generative aperture. This species in many respects assimilates to Agraulina, Bourg. (Lovea tornatellina, Lowe), of Madeira, described aud figured by the Rev. R, Boog Watson (together with Lovece melampoides, triticea, |