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Show 1881.] LAKES TANGANYIKA AND NYASSA, ETC. 2/9 very beautiful, but only visible under a powerful lens. It is a larger species than H. pyramidea 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 volutions is an interesting feature. The west-coast species, which is known under the three names H. pellucida, Gould, H. troglodytes, Morelet, and //. africana, 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. H E L I X ( T R O C H O N A N I N A ) M O Z A M B I C E N S I S , Pfeiffer, var.? (Plate XXXII. figs. 3, 3 a.) Helix {Trochonanina?) mozambicensis, Pfeiffer, P. Z. S. 1855, pi. 31. f. 9 ; NTovitates Conch, iii. pi. 108. f. 1-3 ; var., figs. 4-6. Hab. Between Lake Nyassa and the east coast (Thomson). Only 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 the much greater width of the umbilicus, 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 millims., and its height scarcely 6. 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, Panjan, Kitui in Ukamba, and Tette. 5. HELIX (TROCHONANINA) JENYNSI, Pfeiffer. Helix {Trochonanina?) jenynsi, Pfeiffer, 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 10|. 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 costulae extending from suture to suture; the latter are transversely striated on one side only, namely that nearest the aperture. Body-whorl glossy beneath the periphery, exhibiting faint lines of growth. Aperture large, sublunate ; lip oblique, arcuate and prominent above, and very widely sinuated beneath, thin. Columella somewhat expanded at the upper part. Height 30 millims., diam. 33 ; aperture 17^ long, 15 wide. LLab. Between Lake Nyassa and the east coast {Thomson). |