8 



PROCEEDINGS OF THE ACADEMY OF 



[Jan., 



This species is closely related in shell characters to the type of 

 the genus Uncancylus. Since the teeth are unknown in that and 

 other groups of South American Ancylidae, and the system of the 

 family, as developed by Dr. Bryant Walker, is largely based upon 

 the modes of specialization of the teeth, its dentition becomes of 

 interest. 



Fig. 4. Left and upper figures, U. calverti. Right and lower figures, U. ameliae. 



In U. calverti there are 21-1-21 teeth in nearly straight trans- 

 verse rows. The central tooth is bicuspid, the cusps very short, 

 deeply separated. The laterals have three major cusps, the ento- 

 cone and mesocone more or less united; between them and the 

 ectocone there is a minute accessory cusp. Outside of the ecto- 

 cone there is a minute cusp in the inner laterals, then two, and in 

 the middle teeth of the lateral series, four or five little cusps. In 

 some teeth a minute cusp appears between mesocone and entocone, 

 and in the median and outer laterals another arises on the inner 

 side of the entocone. The laterals are rather widely spaced, more 

 so towards the edges of the radula. The basal plates are shorter 

 than the cusps and very indistinct. 



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Fig. 5. — Uncancylus calverti, half row of teeth. 



The jaw is long, slender, of wide, very short plates and with no 

 lateral processes. 



On comparison with the series of illustrations of Ancylid teeth 

 prepared by Walker it is obvious that Uncancylus is closely related 

 ito the African genus Burnupia Walker. Except for the greater 



