138 PROCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



be partly due to their common Stenogyroid ancestor having 

 developed more or less carnivorous habits. This hypothesis is 

 supported by a study of the embryonic radula of Krapfiella 

 mirabilis ; for, as we have seen, the lengthening of the teeth, and 

 especially of the mesocones, has not taken place in the early rows 

 of the embryonic radula, and only to a limited extent in the later 

 rows. Further, we find that the endocones that occur so frequently 

 in the Stenogyrinse are present towards the front end of the radula, 

 though later they become converted into the broad inner flanges of 

 the mesocones. Thus, in its development the radula seems to 

 recapitulate to some extent the characters of its probable progenitors, 

 and to suggest that Krapfiella and Pseudoglessula have sprung 

 from a more typical Stenogyroid ancestor. 



