212 Transactions of the Royal Society of South Africa. 



find in the Taenioglossa, but four of the teeth are much smaller than the 

 others. The central tooth has seven short cusps, of which the middle one 

 is the broadest ; its basal plate is large but very thin. On each side of the 

 central tooth, but quite separate from it, there is a small narrow tooth, 

 having a curved, thickened edge without any distinct denticulations. 

 Next there is a much bigger tooth, with a long basal plate slightly thickened 

 at the posterior edge, and five cusps, of which the middle one is rather 

 large. On the outer side of this there is another small, somewhat diamond- 

 shaped tooth, without any distinct cusps. The fourth tooth on each side 

 has a very long, rather narrow basal plate, and about nine pointed cusps. 

 Lastly, the marginal tooth has a long and broad, but thin, basal plate, and 

 a row of about thirty minute cusps or denticles. The transverse rows of 

 teeth are only -0115 mm. apart, and the teeth of one row are therefore very 

 largely overlapped by those of the row behind. 



The radula of this species agrees with those of A. hifasciata Nev., 

 A. ovata (Krs.), etc., in having no basal denticulations on the sides of the 

 central teeth. Nevertheless it differs from the radulae of these species and 

 of the more typical members of the genus in several important respects, 

 such as the presence of small additional teeth on each side of the central 

 tooth, the relatively longer basal plates and smaller and more numerous 

 cusps of most of the teeth, and the much greater extent to which the trans- 

 verse rows of teeth overlap one another. Indeed, even under the low power 

 of the microscope, the radula of this species has such a different appearance 

 from those of most species of Assiminea that it would not be surprising if, 

 when the rest of its anatomy has been studied, this form should prove to 

 belong to a distinct, though probably allied, genus. 



Family TRUNCATELLIDAE. 



Genus Truncatella Risso, 1826. 



Truncatella teres Pfr., 1856. 



1856. Truncatella teres Pfr., P.Z.S., p. 336. D. 

 Hab. Mozambique. Querimba I. (Peters). 



Family NERITIDAE. 



Genus Theodoxus de Montfort, 1810. 



Theodoxus knorri (Reel.), 1841. 



1849. Neritina knorri Reel., Sow., Thesaurus Conch, ii, p. 511, pi. Ill, 

 fig. 78 ; pi. 113, fig. 150. D.F. 



Hab. L. Marques. Inhambane (Peters). 



