202 Transactions of the Royal Society of South Africa. 



remain undivided and larger than the other cusps. The transition from the 

 lateral to the marginal type of tooth is gradual and ill defined. The trans- 

 verse rows of teeth trend very slightly forwards on each side of the middle 

 line. The radular formula is : (8+10+1 + 10+8) X more than 90. 



The marginal teeth in this species are of a slightly different type from 

 those shown in Bryant Walker's figures of the radulae of other African 

 Ancylidae,* the cusps being farther from the anterior edges of the teeth and 

 the mesocones larger in proportion to the other cusps. Somewhat similar 

 marginal teeth, however, are possessed by some of the American species of 

 Ferrissia, such as F. parallela (Hald.). 



The lateral teeth are a little more like those found in the genus Burnwpia 

 than are those of most species of Ferrissia that have been examined, although 

 the forms of teeth possessed by these two genera seldom differ very greatly 

 from each other. Walker states that in Ferrissia, and in the subfamily 

 Ferrissiinae as a whole, endocones are wanting ; | but these statements 

 appear to be erroneous. In Burnwpia, a genus which is placed in the 

 Ferrissiinae by Walker, he himself states correctly that endocones are 

 present, more or less united with the mesocones in the lateral teeth. In 

 Ferrissia the endocones seem to be usually more distinct than in Burnwpia, 

 being either separate from the mesocones in the lateral, as well as in the 

 marginal teeth, or merely united with them basally, as in the present species. 



The nearest recorded approach to this species appears to be a single 

 example from Damar, Transvaal, figured by Walker J as a form of his 

 F. cawstoni, from which form it differs chiefly in the curve of the left 

 lateral margin. F.junodi dift'ers so widely, however, from typical cawstoni, 

 that if it happens to be conspecific with the Damar shell, the latter certainly 

 requires a distinct specific name. 



Family POMATIIDAE. 



Genus Tropidophora Troschel, 1847. 



Subgenus ligatella von Martens, 1880. 



Tropidophora {Ligatella) anceps (Mts.), 1878. 



1878. Cyclostoma anceps Mts., Monatsb. Ak. Wiss. Berlin, p. 288, pi. 1, 

 fig. 4. D.F. 



Hab. L. Marques. Andrada (Vasse). 



A large species, described from Taita, Kenya Colony, and fairly common 



in East Africa. 



* " The Ancylidae of South Africa," 1923. 

 t Ibid., pp. 14, 67. 

 X Ibid., pi. 2, fig. 6. 



