Peterson: Miocene Beds of Nebraska and Wyoming. 37 



Greatest vertical diameter of the zygomatic arch 95 



Greatest diameter of the jugal below the middle of the orbit. 30 



Antero-posterior diameter of the orbit 36 



Vertical diameter of the orbit 34 



Length of superior dentition 170 



Distance from incisors to Mi 108 



Length of the molar series 78 



Length of the inferior dentition 175 



Distance from incisors to M T 90 



Length of molar series 87 



Merychyus harrisonensis, 12 sp. nov. 

 (Type. No. 1 341 Carnegie Museum Catalogue of Vertebrate Fossils.) 



This species is established on a fairly well preserved skull which has 

 been somewhat crushed vertically and is without the lower jaws. The 

 type represents an animal a little larger than Merychyus elegans Leidy, 

 and was found in the Lower Harrison beds on Vantassel Creek, Con- 

 verse County, Wyoming. 



The skull is mesencephalic. The occiput is broad and rather low, 

 which is perhaps partly due to crushing. The posttemporal crest con- 

 tinues downward and forward in an uninterrupted and almost straight 

 line to the base of the zygomatic process, thus leaving the base of the 

 mastoid and the external auditory meatus below, but closely adhering to 

 the inferior margin of this crest. 13 The exit of the ear has an upward 

 and backward direction much as in Leptauchenia and Cyclopidhis. The 

 dentition, which is much worn, is apparently less hypsodont than that 

 in Merychyus elegans. 



A closer study of the specimen reveals characters well worthy of 

 note, which may assist in finally determining the value of the species 

 here proposed, when more perfect material is found. 



The occiput is overhanging, which is in part due to crushing. The 

 region above the foramen magnum is deeply excavated. Below and 

 posterior to the posttemporal crests there are deep excavations similar 

 to those in Phenacocoelus. The basicranial axis is gently curved. The 

 paroccipital process is of moderately large size, directed downward and 

 decidedly outward (the latter direction may be due partly to crush- 



12 The specific name indicates the geological horizon in which the specimen was 

 found. 



13 In other genera of the family this crest forms a prominent open angle at the base 

 of the mastoid plate. 



