OCR Text |
Show 1895.] NEW MOLLUSCS FEOM BOENEO. 243 1. Anatomy. Visceral Mass, 8fc.-On removing the shell, the visceral mass presents a single coil (fig. 5), the apical portion being distinct and terminating bluntly. The jaw (fig. 7) is straight and narrow, very slightly concave on the cutting-edge, with a straight central portion less than one-third of the whole breadth. The lingual ribbon (fig. 8) is broad and square, having a great number of equal-sized and similarly-shaped teeth in the row. The lingual ribbon was incomplete in the specimen examined, but the following were counted:-175-1-175. The central tooth is elongate with three points close upon the same level, fleur-de-lis in form, contracting below this and widening again at the base. The succeeding lateral teeth are all uniform, curved, very elongate, with two closely-set points, the outermost being rounded and the innermost sharp and pointed. Generative, Organs (tigs. 9-12).-From the somewhat large thick-walled vagina the penis passes off; its first third is a thick muscular- walled tube which dilates into a more sac-like portion, above which it becomes suddenly constricted, aud then dilates into a bulbous head (figs. 10 & 11). Attached to the upper portion of the penis, above the vas deferens, is a short but strong retractor muscle (figs. 10 & 11, r.m.). From the side of the bulbous head of the penis the vas deferens passes off as a thick tube narrowing gradually as it approaches the prostatic portion of the common duct. The free oviduct commences immediately above the opening of the receptaculum seminis, this latter organ opening into the vagina; it is a small ovoid sessile body (fig. 9, r.s.). The first portion of the free oviduct (fig. 9, ov'.) is thrown into a series of constrictions. The oviduct is a wide tube and densely folded, the prostatic and oviducal portions terminate in a bulbous head lying immediately in front of the globular albumen-gland. The hermaphrodite gland is almost circular and appeared flattened, showing a slight- fold or indentation in the centre. The amatorial organ is a large, wide, thick, muscular-walled tube, making a single coil above the middle half, which would increase its elasticity and act like a spiral spring; just below this is the calcareous dart. Its basal portion is funnel-shaped, the dart itself being long and pointed (fig. 12). 2. Affinities. Damayantia smithi is in every way a most interesting species, differing in many important particulars from Girasia and its allies of the Indian Eegion, of which the following may be mentioned:- 1. The spiral form of the visceral mass is very noticeable, and we probably have here indicated a relationship with forms having a more perfect spiral shell. In Girasia, when the shell is removed, this is not apparent. 16* |