150 Transactions of the Royal Society of South Africa. 



The jaw seems to be composed of a number of fibrous plates, as in other 

 species of the Punctinae. 



The radula (text-fig. 15) is long in proportion to its breadth, measuring 

 •625 X -125 mm. when flattened out. The central teeth are tricuspid, but 

 rather narrow, with oblong basal plates. Their mesocones are less than half 

 the length of the basal plates, and their ectocones are extremely small. 

 The lateral teeth are not so narrow as the central teeth. Their mesocones 

 are about half the length of the basal plates, while their ectocones scarcely 

 exceed half the size of the mesocones. In addition to these two principal 

 cusps, each lateral tooth has an exceedingly minute endocone on the inner 

 side of the mesocone, and two other minute cusps, one between the mesocone 

 and the ectocone and one external to the ectocone. The basal plates of the 

 inner lateral teeth are rather long, and taper somewhat posteriorly, their 

 inner edges being oblique, while their outer edges are roughly parallel to the 



Text-fig. 15. — Punctam hottentotum (M. and P.), Belle Vue, Upper Mooi River, Natal. 

 Half of a transverse row of teeth from the radula ; X 1400. 



length of the radula. In the outer teeth the basal plates tend to become 

 shorter, and they are broader posteriorly, as their outer as well as their inner 

 edges are oblique. In the central and inner lateral teeth the basal plates 

 are hollowed towards their posterior edges, which are consequently ex- 

 ceedingly thin in the middle. Towards the outer margins of the radula the 

 teeth not only become gradually smaller, but they also become shorter, and 

 their cusps become relatively longer and narrower, the minute endocones 

 being rather more developed. In fact, the last two or three teeth on each 

 side resemble the transitional teeth of such forms as Endodonta (Afrodonta) 

 novemlamellaris ; but true marginal teeth can scarcely be said to occur 

 in the present species. The transverse rows of teeth trend slightly forwards 

 on each side. The radular formula is : (15+1 + 15) X 105. 



The radula of another specimen is a little smaller, measuring -525 X -115 

 mm. Its formula is : (14+l + 14)x 94. 



Although this species has hitherto been usually placed in the genus 

 Trachycystis, its radula shows that it belongs to the Punctinae. It differs 

 from Punctum pygmaeum (Drap.) and P. pallidum Conn., in that the meso- 

 cones of the lateral teeth are considerably larger than the ectocones ; but 

 in this respect it agrees with some of the other members of the group, such 



