468 



Revieivs — Prof. Edward D. Cope — 



rises near to the condyle. The cerebral hemispheres are long and 

 narrow, divided by a long flat eras from the olfactory lobes, which 

 are nearly as wide as the cerebral hemispheres. The affinities of this 

 type are not, however, regarded as absolutely determined. The 

 premolar teeth have a sculpture which is not unlike that seen in the 

 fourth premolar of Ptilodus, yet there are no other reasons for sup- 

 posing it to be marsupial. The characters of the astragalus are not 

 unlike those seen in the Creodonta, but other structures indicate that 

 it was probably ungulate. Three species are known, among which 

 P. rhabdodon is fully described. Its cervical vertebras are as short as 

 in the Elephant. The humerus especially, in its small tuberosities, 

 suggests the Proboscidea, though the animal was only about the size 

 of the Collared Peccary, and is thought to have had much the aspect 

 of the short-necked Bear. The teeth indicate omnivorous habit. It 

 is the most abundant Mammal of the Puerco beds. Many of the 

 other types in this family like the species of Hemithlceus, AnisoncJius, 

 and Haplocomis, are known from little more than the dentition, which 

 varies in the number and form of the cusps of the upper molar and 

 premolar teeth. 



The Phenacodontidaa is an allied group of four genera, in which 

 the teeth have much the same general plan as that just described. 

 Protogonia has but one external lobe in the upper premolar teeth. 

 In Phenacodus the fourth premolar has two external lobes, while in 

 Biacodexis the two external lobes are found in the second, third, and 

 fourth teeth. 



Under. Upper. Side. 



Brain of Phenacodus primcevus. 

 Professor Cope's earlier and brief account of Phenacodus has 

 already been reproduced in the February Number of this Magazine. 

 The detailed description now given is a monograph extending to 

 more than sixty pages. The skull in this type is remarkable for the 

 anterior shortening of the nasal bones, so as to give a superior aspect 

 to the nostrils, and these bones extend back closer to the orbit than 

 is usual in Eocene genera, making a slight approach to the Tapir. 

 The slender premaxillary bones are not united in front ; and the 

 rami of the mandible have no bony union. The cerebral hemi- 



