Cope.] 222 [Dec. 21, 



The external crescents of the true molars present prominent anterior an- 

 gles, which form strong vertical ribs. The first superior premolar has a 

 weak, and the second premolar a very strong internal basal cingulum ; there 

 are no other cingula. The diastema is as wide as the diameter of the canine. 

 The first inferior premolar is one-rooted, and the second two-rooted, and 

 both are longer than wide in horizontal diameter. The middle pairs of in-' 

 cisors are very small ; the external one on each side is much larger, the 

 diameter equaling half that of the canines. The first and second true mo- 

 lars are subequal, and are together longer than the third, which does not 

 quite equal in length the three premolars. The heel of the last molar is 

 not so long anteroposteriorly as each of the other columns. The symphysis 

 is steep, but is everted at the incisive region. 



Measurements. M. 



Length of ramus from heel of m. Ill 065 



' ' of molar series 036 



" of premolar series 016 



" of second true molar Oil 



Width of " " " 006 



Length of third " " 016 



Width of " at front 006 



Length of symphysis in front , 025 



Depth of ramus at first premolar 022 



" " second true molar 025 



Width between superior anterior premolars 014 



Cyclopidius hetekodon sp. nov. 

 This species is represented by a portion of the right maxillary bone, 

 which supports the last premolar, first true molar, and portions of other 

 teeth. It is a smaller form than the B. simus, and differs in several import- 

 ant respects. The infraorbital foramen is single and larger than those of 

 the other species. The fourth premolar, while of the same constitution as 

 that of M. simus, is relatively much smaller, not equalling in the extent of 

 its grinding face one column of the first true molar. The latter is pris- 

 matic, and of usual form. Its external crescents are not produced as in B. 

 simus, so that there are no distinct vertical ribs. 



Measurements. M. 



Diameter of last premolar i anteroposterior 0050 



l transverse .0045 



Diameter of first true molar j anteroposterior 0080 



I transverse 0055 



This species was found with the three preceding in the Upper Miocene 

 of Montana by my assistant, J. C. Isaac. 



Blastomeryx borealis sp. nov. 

 This genus was denned by me in the fourth volume of the Report of 

 Lieut. G. M. Wheeler to the Chief of Engineers, 1877, p. 350, as not cer- 



