No. 8.] COPE ON EOCENE VERTEBRATA OF WIND RIVER. 197 



nal side of the ramus contracts or retreats rather abruptly posteriorly, 

 below the last molar. It presents a slight external convexity below the 

 second and third premolars. The alveolar line rises rapidly posteriorly, 

 so that the last true molar is quite oblique. The second (first) premolar 

 has a considerable heel, which is narrow and elevated on the middle 

 line. The principal cusp is large and compressed, but obtuse, and has 

 no anterior basal tubercle. 



Measurements. 



u. 



Length, of six molars 090 



Length of true molars 055 



( vertical 009 



Diameters second (first) premolars anteroposterior .012 



'transverse 006 



Length of base of first true molar 015 



Width of base of first true molar 009 



Length of base of third true molar 023 



Width of base of third true molar Oil 



Depth of ramus at second premolar 030 



C at front of tooth 039 



Depth oframus at M. Ill J ^^ end of tooth 047 



Dedicated to my friend Arthur B. Brown, superintendent of the Phila- 

 delphia Zoological Garden. 



37. Pachynolophus calciciiltjs Cope. 



LopModon calciculus Cope. 

 American Naturalist, 1880, p. 747. 

 Eepresented by lower jaws of two specimens. Transverse crests of 

 inferior molars not connected by oblique ridges. Last true molar with 

 a very small tubercle-like heel. A weak external basal cingulum; 

 enamel smooth. Third and fourth premolars with wide heels, each 

 with a single low ridge. Length of molar series, .053 ; of true molars, 

 .033 ; of last true molar, .014 ; depth of ramus at penultimate molar, .025 ; 

 diameters of penultimate superior molar at No. 2, antero-posterior, .012, 

 transverse, .014. 



This species is referred to Pachynolophus from its analogy to the P. 

 ventorum in most respects. 



38. Pachynolophus ventorum Cope. 



LopModon ventorum Cope, American Naturalist, 1880, j). 747. 



Larger than the last, and differing in having a large heel of the last 

 true molar, and an elevated external tubercle on the heel of the fourth 

 premolar. Enamel wrinkled; no external cingulum. Second jiremolar 

 with a very short heel with an acute tubercle. Length of molar series, 

 .064; of true molars, .040; of last true molar, .016; depth of ramus at 

 second premolar, .020 ; at third true molar, .030. Seven individuals in 

 the collection, one with complete series of maxillarj' teeth. These in- 



