1881.] LAKES TANGANYIKA AND NYASSA, ETC. 287 



equal granular ridges. Base concave near the circumference, then 

 slightly conve.x, concentrically granosely ridged, the ridges nearest 

 the nnibilicus coarser than the others, and also arcuately radiately 

 striated. Aperture irregularly subcircular, whitish. Outer lip 

 (viewed laterally) obliquely incurved. Basal and columellar mar- 

 gins 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. 



Hah. 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. 



Hub. 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 conse- 

 quent increase or decrease in the size of the aperture. 



24. LiTHOGLYPHUs NERiTiNOiDES. (Plate XXXIIL 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 

 ^ 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 &\ milUms., greatest diameter 5 ; aperture 5 long, 3 broad. 



Eab. Lake Tanganyika {Thomson). 



This species resembles L. rufofilosus in its style of ornamen- 

 tation only, in other respects being totally distinct. The form 

 reminds one of certain small species of Neritina ; and on tliat ac- 

 count 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, 



