8 
PATAGONIAN EXPEDITIONS : PALEONTOLOGY. 
Fig. 4. 
A, Hegetotherium mirabile , right hind foot, x f (No. 15,542); B, Nesodon imbricatus, right 
hind foot, about x ^ (No. 15,460). 
Although the molars of Nesodon (text figs. 5, B ; 6, B) appear exceedingly 
complex, owing to the development of secondary enamel folds, the primary 
elements can be homologized with those displayed in the simpler crown- 
pattern of Protypotherium, as indicated by the similar lettering in the 
figures. This comparison cannot, at present, be extended to the other 
Santa Cruz genera, as unworn molars of Hegetotherium , Pachyrukhos 
and Interatherium are not available. Nesodon differs from the Typo- 
A, Protypotherium sp., unworn M- 2 -, x | (No. 9482 American Museum) ; B, Nesodon imbri- 
catus, second and third upper molars slightly worn, x f (No. 15,135). etc, antero-internal cres- 
cent ; pc, postero-internal crescent ; e, ectoloph ; c, crista ; pp, posterior pillar. 
