150 Annals of tJie South African Museum. 



The dimensions vary from : 



Alt. max. 24-4; diam. 24'5 ; apert. 13'GxlO'l mm. 

 to ,, 22-3; ,, 20-2; ,, 11-5x9-2 mm. 



I have also seen a very bleached example, apparently referable to 

 this species, from Kaitop. 



Probably T. <////w////.s is a relatively primitive member of the 

 genus. In its internal anatomy it possesses very few distinctive 

 characters which are not shared by one or other of the remaining 

 species, but in no other form do we find all these features combined. 

 Perhaps it is most nearly related to T. rosaceus, but it differs from 

 that species in its short vagina, swollen hermaphrodite duct, and a 

 few other characters. From T. <jlol>uli<K it may be easily distinguished 

 by its jaw, epiphallus, and penis ; while the coloration of the animal 

 at once separates it from T. namaqiiensis, which it somewhat re- 

 sembles in the lobes on its mantle-edge and in its internal 

 anatomy. The number of transverse rows of teeth in the radula of 

 this species is larger than in any other known member of the genus, 

 and in this respect T. cjypsinus resembles Dorcasia. 



The animals were received too late for illustrations of their 

 anatomy to be included in Plates IV. and V., but the accompanying 

 text-figure shows some of their more important characters. 



TRIGONEPHRUS ROSACEUS (Miiller). 

 (PI. II, f. 4, 5. PL IV, f. 10, 18. PL V, f. 2.) 

 1774 Helix rosacea, Mull., Verm. ii. p. 76. D. 



Shell large, globose, umbilicate, fairly solid, translucent, shading 

 from pinkish buff on the earlier, to bluish violet on the last whorl ; 

 interior nacreous blue, aperture and paries purple-brown . Spire but 

 little produced; apex rounded. Whorls 5, very convex, rapidly 

 increasing, all but the apical covered with close, straight, regular, 

 transverse striae, and showing occasional traces of close, faint, spiral 

 sculpture ; upper surface strongly malleate. Suture deep, subcrenu- 

 late. Aperture lunate ; peristome thickened and reflexed, ends joined 

 by a very slight callus ; outer lip making with the body-whorl an 

 angle of 105. Columella obliquely concave, margin half concealing 

 the deep umbilicus. 



Dimensions of a fairly typical specimen from between the Holgat 

 and Orange Eivers : Alt. max. 39'2 ; diam. 42-0; apert. 24'5x20'5 

 mm. ; ends of peristome 16'5 mm. apart. 



Animal of the same specimen. 



Colour (in alcohol) light grey, darkest towards the hind end of 



