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THE AMERICAN NATURALIST [Vol. XLI 



latter, the ectoloph is simpler, and the internal tubercle is cresceutic, 

 as in the Artiodactyla, the posterior and anterior horns he'm^^ firmly 

 united with the ectoloph so as to form, of the median valley, a deep, 

 but rapidly sloping ])it. This is l)e>t seen in ini unworn tooth. 

 The upper molars, especially uiid M\ in Morojxis arc relatively 

 longer and narrower than in Chalicothcrium (joldjussi . 'i'lie teeth 

 in the latter species appear to have more nearly the same propor- 

 tionate diameter as in the Asiatic forms C. dense and C. sivalense} 

 The more important differences between C. sivalense and C. siense 

 as pointed out in Professor Owen's paper (1. c. pp. 431-432) are 

 as follows: "the anterior part of the interval between the post- 

 external (b) [b ^ reference to the illustrations in Owen's paper] 

 and the postinternal fd) lol)es is not closed l)y a ridge descending 

 from the summit of tlu^ posicxKM-nal lobe as in ('halicofheriiim 



in so ridge-like a way as in Chalirotht rl inii siralviisr." The con- 

 dition of the y)ost-external and post-internal lobes, as well as the 

 "ridge-like" ant-external lobe of M"* in Moropus agree more 

 closely with Owen's statement of C. sivalense; and M., in Moropus 

 is very nearly of tlu^ same size and of the same general character 

 as that in ('. (johljussi. but th.^ relative diameters together with 

 other less imi)ortant .liU'erenees of M ' in the I'airopean and Asiatic 

 forms, is entirely inilike those in Moropus.' 



Phylogeny.— The best evidence at the ])rest iit time }toiius rather 

 towards a European^ than an America!) ancestry of Moi-opn>. 



