.] 



SINCLAIR— THE SANTA CRUZ TVPOTHERIA. 



73 



extended to the other Santa Cruz genera, Hegetothcrium, Pachy- 

 rukhos and Interatherium, as unworn molars of these are not avail- 

 able. Kesodon differs from the Typotheria in the enlargement and 

 caniniform character of the second incisor above and the third below, 

 while in the Typotheria the median incisor in both jaws is the only 

 one tending toward great increase in size. In none of the Santa 

 Cruz Typotheria is there a trace of the double deciduous dentition 

 characteristic of Nesodon. 



oc. 



Fig. 8. A. Unworn third upper molar of a young Protypothcrium, four 

 and one half times the natural size. (No. 9482 American Museum of Natural 

 History collection.) B. Nesodon imhricatus Owen, second and third upper 

 molars slightly worn, three fourths the natural size. (No. 15135 Princeton 

 University collection.) ac, antero-internal crescent; pc, postero-internal 

 crescent; e, ectoloph; c, crista; pp, posterior pillar. 



From these resemblances in dentition and foot structure it seems 

 permissible to infer that the Toxodonta and Typotheria had a com- 

 mon origin, but the facts at present available do not justify us in 

 saying more. 



2. With Typotherium. — Difficult as it is to ascertain the relation- 

 ship existing between the Santa Cruz Typotheria and the Nesodons, 



