110 



Annals of the South African Museum. 



the upper edge of each tooth and in a slanting direction. A transi- 

 tion to the marginal type of tooth is effected by the appearance on 

 or about the thirty-fifth tooth of a small interior cusp on the acutely 



KM MM UM/ 



FIG. 1. 

 Marinula tristanensis. Radula. (4 x yV Homog. imm.) 



pointed second cusp. The latter gradually divides into two and 

 eventually more cusps appear until at about the 90th tooth four or 

 five small, equal cusps are found arising from a somewhat amorphous 

 basal plate. 



The radula thus described clearly is distinguishable from that of 

 Melampus and Phytia, although a family likeness is obviously 

 present in all three. 



The jaw (Fig. 2) is a typically Auriculid structure consisting of 

 numerous loosely arranged fibres. It differs from that of Melampus, 

 however, in being of a regular gently arcuate form slightly upturned 

 at the extremities. At the latter the fibres are better developed and 

 more regularly arranged than in the median area of the jaw. 



The genitalia (Fig. 3). The organs of reproduction do not 

 offer any singular departure from the usual Auriculid type although 

 they are substantially different in disposition and form from those of 

 Melampus, Phytia, and Pythia. 



FIG. 2. 

 Marinula tristanensis. Jaw. (4 x 6 obj.) 



The male genitalia do not differ very markedly from those of the 

 three genera alluded to above in the presence or absence of any 

 essential part. On the whole it is more like the slender delicate 



