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Show 1881.] LAKES TANGANYIKA AND NYASSA, ETC. 287 equal granular ridges. Base concave near the circumference, then slightly convex, concentrically granosely ridged, the ridges nearest the umbilicus coarser than the others, and also arcuately radiately striated. Aperture irregularly subcircular, whitish. Outer lip (viewed laterally) obliquely incurved. Basal and columellar margins forming one strongly arcuate line joined above to the extremity of the labrum by a thickish callosity. Operculum unknown. Length 15 millims., greatest diameter 18. Hab. Lake Tanganyika {E. Coode Hore). This is perhaps the most remarkable shell of the entire collection. It is perfectly trochiform in general appearance; and the character of its sculpture agrees with that which obtains in many species of that family. I have much pleasure in assoeiating with it the name of Dr. John Kirk, who has been a most liberal donor of specimens to the Museum, and has done much to advance our knowledge of the fauna and flora of East Africa. 23. LITHOGLYPHUS ZONATUS, Woodward. Lithoglyphus zonatus, Woodward, Proc. Zool. Soc. 1859, p. 349, pi. 47. f. 3-30 ; Smith, P. Z. S. 1880, p. 350. Hab. Lake Tanganyika {Thomson). Several specimens of this species tend to show that it is subject to little variation, the only difference of any importance consisting in the greater or less contraction of the last volution and the consequent increase or decrease in the size of the aperture. 24. LITHOGLYPHUS NERITINOIDES. (Plate XXXIII. fig. 19.) Lithoglyphus neritinoides, Smith, Ann. & Mag. N . H. 1880, vi. p. 426. Shell ovate, imperforate, thinnish, smooth. Spire short, purplish, whitish beneath the suture. Whorls 4, convex ; last one large, elongate, semitransparent, whitish, covered with an intensely thin subolivaceous epidermis, ornamented with thread-like transverse red lines. Aperture inversely pyriform, occupying a little less than f- of the entire length of the shell. Outer lip thin. Columella coated with a large callosity, extending from the upper extremity of the labrum to the base of the aperture, and spread considerably over the whorl in the umbilical region. Operculum unknown. Length 6 J millims., greatest diameter 5 ; aperture 5 long, 3 broad. Hab. Lake Tanganyika {Thomson). This species resembles L. rufofllosus in its style of ornamentation only, in other respects being totally distinct. The form reminds one of certain small species of Neritina; and on that account the specific name selected bears reference to that genus. The great development of the columellar callosity is very remarkable. All three specimens exhibit a dark transverse stain on the back of the body-whorl at a short distance from the suture; but whether or not this is a permanent character requires more examples in proof. |