17G 



EVOLUTION OF MAMMALIAN MOLAR TEETH 



mesostyle 



hypocone-"^ 



iantecrochet 



D 



i 

 i 



FIG. 163. Cusps, Crests, Styles, Crochets, and Fossettes in the molar teeth of the Horse. 

 The specimens figured belong to a North American Pleistocene species, Equus complicatus. 



A. Unworn crown. 



B-D. Successive stages of wear. All figures natural size. 



The Tapiridne, as shown in Figs. 172-174, develop a sub-lophodont 

 dentition, the protoloph and nietaloph being well developed, while the 

 ectoloph does not form a completely united crest. 



In the Khinocerotida? we have the extreme lophoid evolution, in 

 which the crown consists of the completed proto-, meta-, and ectolophs 

 (Figs. 175-182). 



