No. 480] EXTINCTION OF MAMMALIA 



847 



(1873, p. 152) the extinction of all Artiodactyla with an inadaptive 

 foot structure and inadaptive grinding teeth as follows: Upper 

 Eocene, Xiphodon, Anoplotherium, Diplopus; Oligocene, Hvopo- 

 tamus, Anthracotherium, Entelodon. He pointed out that the 

 inadaptation of the foot in these animals consisted of a mechanical 

 defect in the manus (3d metacarpal not spreading above to articu- 

 late with the trapezium as in the 'adaptive' manus of the pig and 

 hippopotamus, see Taf. 7), and that the inadaptation in the grinders 

 consisted of the persistent short or brachyodont crowns, buno- 

 selenodont and bunodont, composed of partially rounded cones. 

 These feet being mechanically weak in the function of the carpals 

 and metacarpals were incapable of the elongation into cannon 

 bones — a cursorial or speed adaptation which saved the lives of 

 the adaptively reduced Artiodactyls. These short teeth were by 

 his theory not adapted to a supposed change of vegetation from 

 softer herbage to harder Gramineae. His paleozoological sup- 

 position that such a change of food occurred was independently 

 confirmed by the j)ale()i)()tanists Sa]H)rta and Marion. Ilis eon- 



since been al.nn(hintlv <-onlinne.[ hv Mibse"(|uent observations of 

 the extinction of all forms of (,ua.irnpe.ls with tliese inadaptive 

 typ<-s of .short-croune.l grinders both in North America and in 

 hulia. 



This uvnerali/ati.>n is notewortliv also as l.earino- uf.on the 

 extinction of the Titanotheres (Oligocene) and Clialicotheres 

 (Upper Mi<.cene) types, both of wl'iich possess short-crowned 

 bunoselenodont niohirs. 



been recognized by every author who has written u})on these 



selenodont or combined cont-and-crescent ])attern of griniling 

 teeth, were adajited to browsingon coarst- an<l soft rather than fine 



