476 Reviews — Prof. Cope — Tertiary Vertebrata of the West. 



Triplopus, owing to the second metacarpal having a considerable 

 contact with the os magnum. The bones of the hind limb have 

 most resemblance with Hyrachyus ; but the femur of Hyracotherium 

 has the great trochanter larger, so as to project far above its head. 

 The third trochanter is large, but not so long as in the Tapir and the 

 Horse. The species range in size from H. index, which is equal to 

 the Kit Fox, to H. craspedotum, which is equal to the Co}'ote. Three 

 species are found in the Wasatch beds, three in the Wind River beds, 

 and one in the Bridger beds. 



The genus Plioloplius is said to differ from Hyracotherium only 

 in having two tubercles on the heel of the fourth premolar tooth 

 instead of one. The genus is intermediate between Hyracotherium 

 and LopJiiotherium. Six species have been defined, including Professor 

 Owen's original type, and five of these are North American. The 

 genus Heptodon is essentially a Lophiodon with seven superior molars : 

 three species are now described. Hyrachyus has no heel to the last 

 true molar; its lower canines form a continuous series with the 

 incisors, but are separated from the premolars by a diastema. The 

 affinities of the skeleton are, first, with the Rhinoceros type; secondly, 

 with the Tapirs, and least with the Horses. Equine characters are 

 seen in the articulation of the lumbar vertebrae, Rhinocerontic charac- 

 ters in the form of the sternum ; but the affinities are strongest with 

 Hyracotherium. The carpal articulation of the ulna is not so small 

 as in Triplopus and Anchitherium. Nine species have been recognized ; 

 three are fully described, and the author points out in detail the 

 differences between Hyrachyus eximius and Tapirus roulini. Triplopus 

 is a genus nearly allied to Hyrachyus in its dentition, but appears to 

 have a third transverse crest in the first true molar, and there is a 

 difference in the number of digits in the fore foot. The rudimental 

 character of the fifth metacarpal, which in Hyrachyus is well 

 developed, and carries a digit, is the ground for making Triplopus 

 the type of another family. It is regarded as connecting the Lophio- 

 donts with the Rhinoceroses ; but the structure of the true molars 

 and the character of the feet place it between those families. Only 

 one species is known with certainty. 



A synopsis is given of the generic characters of the Rhinocerida?, 

 based on the number of digits, the dentition and the conditions of 

 the skull connected with the development of horns. The Tapiridaa 

 is in the same way briefly defined, but no species of either group is 

 described. 



The Chalicotheriidse is a group of eight genera. The symmetrical 

 external Vs of the upper molars and the double Vs of the inferior 

 molars distinguish them from the Lophiodontidee ; but they are not 

 so clearly defined from the Menodontidse. Among its genera, Pachy- 

 nolophus and Chalicotherium are found in Europe, Nestor itherium in 

 Asia, while North America yields Ectocion, Leurocephalus, Palozo- 

 syops, Lymnohyus and Zambdotherium, all of which are defined by 

 dental characters. Ectocion is only known from the teeth ; Palceo- 

 syops differs from Palceotherium in the isolation of the internal cones 

 of the upper molars from the external longitudinal crescentic crests, 



