AMBLYPODA. 509 



The relationships indicated by the brain are to the lissencephalous 

 orders CJdroptera, Insectivora, and Edentata. As an ungulate oixler, the 

 Amhhjpoda are distinguished from the first two, were other characters 

 wanting. We may here notice, however, some curious resemblances 

 between the forms of the teeth and lower jaw of Conjphodon and Bathjopsis 

 and some Insectivora, and the still more curious resemblance between the 

 tibio-tarsal articulation in the order and that of the cotemporary Creodont 

 allies of the Insectivora. Comparison with the Ungulate forms oi Edentata 

 only is necessary, and from these the enamel sheathing of the teeth sepa- 

 rates the Amhlypoda at once. The small size of the brain doubtless relates 

 these animals to the other Eocene Ungidata described by Lartet, still more 

 nearly than to existing Lissencepliala. In the small size and smoothness of 

 the hemispheres, and relatively large development of the optic and olfactory 

 lobes, the brain of the Amhlypoda more nearly resembles that of the 

 Creodonta than that of any division of recent animals. The resemblance 

 between the brains of Amhlypoda and those of the Carnivorous Arctocyon 

 {fide Gervais) is so great as to testify to a similar degree of cerebral develop- 

 ment in both the clawed and hoofed types of Eocene Mammalia. 



As a resume of the relations of the Amhlypoda, it may be said that 

 they are the most generalized order of hoofed Mammalia, being interme- 

 diate, in the structure of their limbs and feet, between the Prohoscidea, the 

 Perissodactyla, and the Artiodactyla. This fact, together with the small size 

 of the brain, places them in antecedent relation to the latter, in a systematic 

 sense, connecting them with the lower Mammalia with small and smooth 

 brains, still in existence; and, in a phylogenetic sense, since they preceded 

 the other orders in time, they stand in the relation of ancestors. It is 

 doubtless true that the Amhlypoda were the ancestors of all living Ungu- 

 lates, although no genus of the latter can yet be traced to any known 

 genus of the former, such genera remaining for future discovery.* Stand- 

 ing in this antecedent relation, comparison with other classes of Vertehrata 

 is in place. The proportionate size of the brain is, in the Dinocerata, as 

 has been discovered by Marsh, more like that characteristic of many 



* A discussion of these and other general relations of the Amhlypoda may be found in a paper read 

 by me hefore the American Association for the Advancement of Science, August, 1875, and published in 

 the Penn Monthly Magazine, December, 1875. 



