1S80.J 



457 



Hyracoidea. 

 Proboscidia. 



LCope. 



Hyrax ; no foramina. 



Elephas ; no foramina. 



Perissodactyla. 

 In this order the number of the foramina ranges from very few to manj', 



Fig. 3.— Aphelops megalodux Cope, Loup Fork of Colorado; one-sixth natural 

 size; showing postparietal foramen. 



BJiinocerus, Aphelops ; postparietal only, 



Fig. 4. 



Fig. 5. 



Skulls of Aphelops megalodus (Fig. 4) and A. fossiffer (Fig. 5) from behind ; one- 

 sixth natural size; showing absence of mastoid foramen. 



Tapirus; postparietal and a huge mastoid. 



AncJiitherium, Hippotfierium, Proto7iippus and Equus ; postparietal, 

 postsquamosal, postglenoid and supraglenoid. In the last three genera 



PROC. AMER. PIIIl.OS. SOC. XVIII. 105. 3g. PRINTED MARCII 6, 1880. 



