GEOLOGICAL SURVEY OF THE TERRITORIES. 605 



the valley below. It wears iuto a i^rominent loop. The anterior cusp is 

 much less elevated than the median, and is separated from the latter by 

 a considerable ridge. The only cingulum on the molars is on the outer 

 side of the first. Enamel smooth. 



Measurements No. 1. 



M. 



Length of five molars 0.071 



Length of three posterior molars 0470 



Length of last molar 0159 



Wiflth of last molar 0200 



Width of penultimate molar 0210 



Length of peuultmiatc molar 0163 



In the more perfect specimen all of the molars have two transverse 

 crests, except the P. M. 1. The lower molars possess strong anterior 

 prolongations of their posterior crests; the third and fourth premolars 

 have one elevated transverse crest near their middle, and the second is 

 much compressed. The first I cannot find. Symphysis rather short 

 for the genus. 



Measurements No. 2. 



M. 



Length of stiperior molar series „ 0. 085 



Length of true molars 046 



Length of penultimate 015 



Width of penultimate Ol'j 



Length of inferior molar series . 078 



Length of inferior true molars „ 047 



Length of penultimate 017 



Width of penultimate Oil 



Width of last premolar 008 



Length of last premolar „„.. . 012 



Depth of ramus at last j)remolar 0235 



Length of diastema 019 



Length of bases of three incisors 018 



Hyrachyus ageaeius, Leidy. 

 Common everywhere. 



Hyrachyus boops, Marsh. 



HelaJetes hoojjs, Marsh, American Journal, 1872, p. 218 ; Hyrachyus hoops, Cope, Oa 



some Eocene Mammals, *fcc., 1873, p. 6. 



Bitter Creek and Black's Fork. 



Hyrachyus nanus, Marsh. 



LopModon vanus, Marsh, American Journal Sciences and Arts, 1871, July; Ryrachijus 

 nanus, Leidv, Geological Survey of Montana, 1871,13. 361; HdaJcics, Marsh, 1. c, 

 1872, p. 218/ 



Cottonwood Creek. 



ANCHIPPODCJS, Leidy. 



Proceedings Academy Natural Sciences, Philadelphia, 1868, x>. 232; Trogosiis, Leidy, 

 Proceedings Academy Natural Science, Philadeli)hia, 1871, and Geological Survey of 

 Montana, 1871, p. 359. 



Anchippodus minor, Marsh. 



Paloiosyops minor, Marsh, .\merican Journal Science and Arts, 1871, July; Trogosus 

 castoridens, Leidy, Geological Survey of Montana, 1871, p. 360. 



Cottonwood Creek. 



