604 GEOLOGICAL SURVEY OF THE TERRITORIES. 



of the exterual seen in H. exhnius. (5) Tlie rotnlar groove is also nar- 

 rower in tlic hitter and not so deeply excavated as in T. roulini. 



The tibia is (1) reduced in size, and especially contracted distally ; the 

 relative widths of the ends are 6 era : 3.5; in T. roulini 7.5 cm to 5. {2) 

 The crest is more prominent, and is deeply fissured l)ya groove' which 

 is represented by a shallow concavity in T. roulini. The groove (3) ex- 

 ternal to this is deeper. (4) The posterior inner tuberosity of the distal 

 end is more median, hence the inner trochlear groove is further removed 

 from the anterior inner malleolus, which has, therefore, a greater inner 

 (not outer) extent. 



The tarsus (1) is generally longer and narrower, except in the case of 

 the cuboid bone, (2,) which is shorter than in T. roulini. (3) The astra- 

 galus has a narrower neck, which, therefore, appears more on the inner 

 side, (i) The facet for the cuboid is smaller. (5) The inner tuberosity 

 of the head is more i^rominent. (G) The calcaneumismore slender, with 

 larger cuboid facet, especially posteriorly. The metatarsus is absolutely 

 nearly as long as in T. roulini, and, therefore, relatively longer and more 

 slender. (2) The median (III) is nearly similar to the others in width; 

 in the T. roulini, much larger than the lateral. 



T\\p phaJamjes of the first cross series are more contracted distally. 



The more important differences between the skeleton of the two species 

 in addition to those pointed out under the head of the genus, are those 

 of the ulna, the scapula, the lumbar vertebne, the ilium, and the crest 

 of the tibia. The scapula is more like that of Tapirus /erre«^rw, while 

 the ilium is approximated by that of T. malayanus among living species; 

 its form leans toward the Equine series, and not to the Palieotheroid. 



Conclusion. 



From the preceding it is evident that there lived in North America 

 during the Eocene period a type of Tapiridw only difl'ering generically 

 from that now existing in South America. Thus one form of the many 

 peculiar and primitive ones of that time still persists in the tropics and 

 southern hemisphere, which claims more ancient character than the 

 rhiuocerus, elephants, and other remains of Miocene time. 



The afiinities of Cercolepies and Nasua to the types of the same period 

 have been already indicated,* and with the present case may be regarded 

 as confirmatory of the proposition stating the early geological state of 

 the existing Fauna Neotropica.f 



HYRACHyus iMPLicATUS, Cope. 



Ou some Eocene Mammalia, &c., 1873, p. 5; published March 8. 



This taf>ir is smaller and more slender than the S. agrestis, Leidy, but 

 exhibits an equal size of posterior molar teeth, which are thus relatively 

 larger than in that species. It is represented first by both maxillary 

 bones, with most of the molars complete, Irom Cottonwood Creek, 

 Wyoming; then by the side of the face, with molars of both jaws com- 

 plete, with symphysis and portions of all the incisors, from South Bitter 

 Creek, and by i)art of mandibular ramus, with teeth, from Green River, 

 "with probably other specimens. 



The molars differ from those of the other Hyrachyi, and resemble those 

 called Helaletes, in the presence of a i>rominent ridge, which descends 

 on the inner side of the principal (median) outer cusp, not quite reaching 



* See on the Primitive Types of the Mammalian Orders, 1873. 

 t See Origin of Genera, j). 99 and preced. 



