710 THE BRIDGER FADTSTA. 



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. 



Meamirements. 



if. 



Length of six mol.irs 0.090 



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 0i3 



Width of base of third true molar - Oil 



Depth of ramus at second premolar 030 



T-, ., ^ . ,r .••< at front of tooth 039 



Depth of ramus at M. HI < , „ , 



' < at end of tooth 047 



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

 delphia Zoological Garden. 



Lambdotherium popoagicdm Cope. 



American Naturalist, IRtfO^ p. 748. Bulletin U. S. Geological Survey Terrs., VI, 1881, p. 196. 

 Plate XXTX «, fig. 7, and Plate LVIII, figs. 3-5. 



This is the most abundant Perissodactyle of the Wind River beds, 

 remains of at least twenty-two individuals having come under my observa- 

 tion. The general characters of the inferior molars are as follows: The 

 heels of the second and third inferior premolars have a median keel ; the 

 third only has an anterior tubercle. The crest of the heel of the fourth 

 forms an imperfect V. Heel of the last true molar small. No cingula. 

 Enamel smooth. Length of series, .080; of true molars, .044; of last 

 molar, .019; depth of ramus at first premolar, .021 ; at last molar, .031. 



The crowns of the superior molars are very short; their external Vs 

 are well distinguished by an intermediate vertical protuberance, but their 

 external faces are less obliquely sloped inwards than in the species of the 

 genera Lhnnohjus and Palceosyops. Traces of the median ribs on the exter- 

 nal faces of the Vs are slight. The tuberosity which bounds the anterior 

 V ill front is very large, and its apex is continued into the anterior basal 

 cingulum, as in Lopldodon and allies. Its size causes the external wall of 



