254 EOCENE FAU>^E. 



the Gyrencephalous oidei's generally, characterizing only the Perissodactyla. 

 Among Lisaencephalous orders, it is very common in the Edentata, and still 

 more usual in the Insectivora It does not occur among Marsupials. But 

 in the Prosimice, there is often a third trochanter (Mivart, loc. cit.; e. g., Lemur, 

 Galago). In Talpa and some other Insectivora, and also in Chiromys, it is 

 situated high up, nearly opposite the little trochanter. 



The peculiar character of the ankle-joint already mentioned is not 

 certainly characteristic of all the genera of this division. In Mesonyx it is aa 

 perfect a tongue and groove as in the most specialized of existing Carnivora. 

 In the Creodonta of the Wasatch it is on the contrary flat, and resembles 

 moi'e than any other existing type the ankle-joint of the otter. It probably 

 indicates aquatic habits of the species possessing it. 



The comparison of this group brings out principally aflSnities to the 

 Insectivora and Prosimice Besides the differences from the Marsupialia, 

 already pointed out, in the genera Oxycetia and Didymictis, the posterior part 

 of the inferior border of the mandibular ramus is not inflected, as in Marsu- 

 pialia; in Stypolophtis (viverrinus) the lachi'ymal canal is within the orbit, 

 and not exterior to it. The frequently reduced number of incisors in the 

 lower jaw and the normal number above, are a further ground of distinc- 

 tion from the Carnivorous Marsupialia. 



Comparison with the Prosimice shows that the difi'erences consist in the 

 sectorial character of some molar teeth, and large development of the canines, 

 in the Eocene forms ; in the short tarsal bones, and peculiar tibio-tarsal 

 articulation; with convex external face of the ilium. This ensemble of 

 characters can hardly be regarded as ordinal ; and there only remains, to 

 give character to such a distinction, the difference in the size and form of 

 the cerebral hemispheres. This character, in some of the smaller living 

 Lemuridce, is not strongly marked, and in them the approximation to the 

 Lissencephalous Manmials is at its closest. 



The differences from the Insectivora are less numerous. The only 

 trenchant distinctive character upon which I can seize, in comparison with 

 Myfhomys and Solenodon, is the peculiar tibio-tarsal articulation. On this 

 account, and because of the rather more marked camassial characters of 

 the molar teeth, I have proposed to place the genera Aniblyctonus, Oxycetia, 



