OCR Text |
Show 1880.] THE GENUS GIRASIA. 293 from Shillong, all of typical Girasia. These have furnished me with the means of more accurately describing the genus. GIRASIA SHILLONGENSIS, G.-A., J. A. S. B. January 1875, p. 4, pl. ii. f. 1, la. The following will be an emended description of the genus:- Shell rudimentary, horny, narrow, elongate, of one simple whorl; colour olivaceous, apex white, the central portion of the inside of the shell covered with a milky-white callus. About 1 inch long. (Plate XXIV. fig. 10.) Animal slug-like, long, mantle largely developed; shell and dorsal lobes are united all round ; and the shell is entirely covered by the former, with the exception of a narrow area on the posterior left margin. From the anterior right margin of this area a well-marked cicatrical line runs forward to just above the respiratory and anal orifice, and marks the usual division of the shell-lobes in other species into a left (frontal) and right (posterior). The dorsal lobes are divided diagonally forward from trie respiratory orifice into a large left dorsal lobe and (behind and adjacent to the orifices) a smaller right dorsal lobe; on the extreme posterior side a slight beading marks the junction of these lobes with the shell-lobes above. This portion of the animal is sunk into a deep V-shaped depression in the back, where the dorsal ridge of the foot terminates suddenly. Extremity of the foot truncate, with a large linear mucous gland ; the pedal line is very distinct. Genital aperture near the lower and outer base of tbe right tentacle. The foot is divided longitudinally into three subequal median and lateral areas, and is distinctly segmented, the major divisions on the pallial edge of the foot being continued in V-shape from one side to the other, the angle being directed backwards in the spirit-specimen ; but they are co doubt straight when the animal is alive. Generative organs of G. shillongensis.-In every way similar to G. gigas, Bs. The ovo-testis consists of five separate bunches or lobes of very minute globular follicles, each lobe having a separate duct leading to the main hermaphrodite duct; this graduallywidens, and becomes much thickened, with several sharp convolutions; it then suddenly contracts again, leading to the junction of the albumen- gland. Here a short pear-shaped caecum is conspicuous (only seen in one specimen). The albumen-gland was not perfect, but appeared as if formed of two lobes (from above specimen). The prostate was wide, ribbon-like; the oviduct with three or four great folds, which extend to the posterior termination of the spermatheca, which is not so long as to be infolded by it. The vas deferens is given off a very short distance below the end of spermatheca, high up the oviduct ; and it extends backwards to near the base of the penis and amatory organ, in a loop, to join the former close behind a caecum-like appendage rounded at the end (the caecum calciferum). The penis is bent on itself, where a long process is given off, to which the retractor muscle is attached. Ihe ama- |