1881. J LAKES TANGANYIKA AND NYASSA, ETC. 279 



very beautiful, but only visible under a powerful lens. It is a 

 larger species tban H. pi/ramidea of Martens, has fewer whorls, and is 

 more depressed and carinate. The depression immediately above 

 the keel of the body-whorl and above the suture in the upper volu- 

 tions is an interesting feature. The west-coast species, which is 

 known under the three names H. pelluckla, Gould, //. troglodytes, 

 Morelet, and H. africaiia, Pfeiffer, is very like this species. It is, 

 however, more coarsely sculptured, with a less flattened spire and a 

 less angulated body-whorl, and lacks the depression above the angle 

 and on the upper volutions. 



4. Helix (Trochonanina) mozambicensis, Pfeiffer, var. ? 

 (Plate XXXII. figs. 3, 3 «.) 



Helix (^Trochonanina) mozambicensis, Pfeiflfer, P. Z. S. 1855, 

 pi. 31. f. y ; Novitates Conch, iii. pi. 108. f. 1-3 ; var., figs. 4-6. 



Had. Between Lake Nyassa and the east coast {Thomson). 



Onlv a single specimen was brought home by Mr. Thomson from 

 the above district. It is distinguished from all the specimens of this 

 species which I have seen by tlie much greater width of the umbi- 

 licus, its coarser arcuate lines of growth, somewhat greater solidity 

 of texture, and small size. It appears to be adult ; yet its greatest 

 diameter is only 11 miUims., and its height scarcely C. These 

 measurements, in comparison with those of the variety albopicta 

 described by Martens, are very small ; for some specimens of the 

 latter form attain a width of 19 millims., with a height ranging from 

 10 to 13. Other localities for this species are near the Albert- 

 Nyanza lake, Zanzibar, Panjau, Kitui in Ukamba, and Tette. • 



.5. Helix (Trochonanina) jenynsi, Pfeiffer. 



Helix {Trochonanina) jenynsi, Pfeiifer, Reeve, Con. Ic. f. 979 ; 

 Pfr. Con.-Cab. pi. 129. f. 23 & 24 ; Philippi, Abbild. ii. pi. 7. f. 8. 



Hab. Between Lake Nyassa and the east coast {Thomson). 



This species has also been recorded from Zanzibar and Pangani. 



The dimensions of the largest shell considerably exceed those 

 of the originally described specimen. Its greatest diameter is 16 

 millims., and the height is lOg. 



6. Streptaxis gigas. (Plate XXXII. figs. 4, 4 a.) 



Streptaxis gigas, E. A. Smith, Annals & Mag. Nat. Hist. ser. 5, 

 vol. vi. p. 429 (1880). 



Shell very large, white, widely umbilicated. Whorls 6, regularly 

 increasing, rather convex, furnished with close, coarse, very arcuate 

 costulse extending from suture to suture ; the latter are trans- 

 versely striated on one side only, namely that nearest the aperture. 

 Body-whorl glossy beneath the periphery, exhibiting f;nnt lines of 

 growth. Aperture large, sublunate ; lip oblique, aicuate and pro- 

 minent above, and very widely sinuated beneath, thin. Columella 

 somewhat expanded at the upper part. Height 30 millims., diam. 

 33 ; aperture 17^ long, 15 wide. 



Ilab. Between Lake Nyassa and the east coast (Thomson). 



