140 Transactions of the Royal Society of South Africa. 



The individual teeth are extremely small. The central teeth are tricuspid, 

 but their mesocones are only about half the length of the quadrate basal 

 plates, and their ectocones are scarcely half the length of the mesocones. 

 In the inner lateral teeth the mesocones are of about the same size as in the 

 central teeth, but they are situated much nearer the inner than the outer 

 sides of the teeth. The endocones of the lateral teeth are very small ; the 

 ectocones, on the other hand, are slightly larger than those of the central 

 teeth. An extremely minute additional cusp is inserted between the meso- 

 cone and the ectocone of each of the lateral teeth. The basal plates of 

 these teeth are shghtly oblique, though of about the same length as in the 

 central teeth. In the transitional teeth the basal plates begin to shorten, 

 and the three principal cusps become longer and more pointed. The mar- 

 ginal teeth are somewhat pectinate in form, the bases being shorter and the 



B 



Text-fig. 9. — Endodonta (Afrodonta) novemlamellaris BurnuiJ, Vengo Mountain. 



A. Kidney, heart, etc., seen from the outside (slightly diagrammatic) ; X 17. 



B. Half of a transverse row of teeth from the radula ; X 1600. 



cusps sharply pointed and more numerous, owing to the ectocones having 

 split up into three or four small cusps and the endocones often into two. 

 In these teeth the endocones are better developed than in the laterals, but 

 the mesocones are still the longest of the cusps. The transverse rows of 

 teeth trend very slightly forwards on each side in the region of the lateral 

 teeth and more decidedly in that of the marginal teeth. The radular 

 formula is: (7+8+1 + 8+6) X 100. 



The radula of this species is specially interesting because, although the 

 marginal teeth scarcely differ from the type most usually found in the 

 Endodontinae, the central and lateral teeth in several features show some 

 approach to the type found in the Punctinae, and thus suggest how this 

 rather peculiar type of radula may have been evolved (compare text-fig. 9, B 

 with text-figs. 15 and 16, B). In Godwin- Austen's figure of the radula of 

 Endodonta {Afrodonta) bilamellaris (M. and P.),* the central and lateral 

 teeth are depicted as of the ordinary type, such as we find in Trach. vengoensis 

 Conn, (text-fig. 14). 



* Ann. Mag. Nat. Hist., ser. 8, vol. i, 1908, pi. viii, fig. 26. 



