152 Annals of the South African Museum 



sculpture is much finer, never approaching the coarse, rib-like 

 striation of the last-named species. 



The aperture, as before mentioned, projects more out to the side 

 than that of globulus, and affords a ready means of distinction. The 

 margins, moreover, are sometimes thickened backwards for as much 

 as 3^ mm., and then squarely grooved, rather than reflexed ; but 

 this feature is quite inconstant, even among specimens from the 

 same locality. 



The large form of T. rosaceus seems to be pretty generally 

 distributed in the neighbourhood of the Lower Orange River, 

 though I have no definite localities for it except Port Nolloth. A 

 smaller form, which from its sculpture and aperture probably 

 represents a local race of the same species, is depicted on PL II., 

 fig. 5. It has only come to hand so far in bleached condition, from 

 Anenous and Koingnaas. 



Judging from the single specimen dissected, the reproductive 

 organs of T. rosaceus differ from those of both the preceding forms 

 in the long vagina, and in the very small extent to which the vas 

 deferens is convoluted. From T. globuhis this species also appears 

 to differ in its jaw, receptacular duct, epiphallus, and penis ; and 

 from T. gypsinus in its mantle-edge, hermaphrodite duct, and vesicula 

 seminalis. 



TRIGONEPHRUS PORPHYROSTOMA (Melv. & Pons.). 

 (PI. II, f. 6. PI. IV, f. 2, 11, 19, 25, 28. PL V, f. 3. Text-fig. 1, A, B.) 

 1891 Helix (Dorcasia) porphyrostoma, M. & P., A.M.N.H. viii. p. 238. D. 



Shell large, slightly elongate-globose, deeply rimate, solid, just 

 translucent, shading in colour from pale pink on the earlier, to 

 bluish grey on the later whorls ; peristome and interior purple- 

 brown. Spire somewhat produced, very nearly as long as the 

 aperture ; apex rounded. Whorls 5f , convex, rapidly increasing, all 

 but the first two faintly and irregularly malleate above, and covered 

 with straight transverse striae, which become coarse and more 

 distant with the growth of the shell, and assume a rib-like 

 appearance towards the aperture. Suture deep, subcrenulate. 

 Aperture quadrate ; peristome reflexed and much thickened, ends 

 joined by a distinct callus ; outer lip making with the body-whorl an 

 angle of nearly 120. Columella erect, margin broadly reflexed, 

 almost concealing the narrow perforation. 



Dimensions of a typical specimen from between the Holgat and 



