PEOSiMi^. 243 



length of the last inferior molar. The length of the posterior four molars 

 of the M. pungens equals that of the three true molars of the M. crassius- 

 culm; and the last true molar of the latter is half as long again as the pen- 

 ultimate, while in M. pungens it exceeds it but little. 



The best preserved true molar is the second. Its most elevated cusps 

 are the anterior and posterior inner, of which the anterior is subconic and 

 more elevated. The anterior external cusp is crescentic in section, and 

 sends crests to the supplementary, anterior inner, and the posterior anterior 

 inner, both of which descend inwards. The posterior crest reaches the pos- 

 terior base of the anterior inner cusp. 



The posterior external cusp is an elevated angle, sending crests forwards 

 and backwards. The former reaches the base of the anterior external cusp 

 (not reaching the inner), while the latter passes round the posterior edge of 

 the crown. As in M. pungens, it is convex posteriorly, and rises to the pos- 

 terior internal cusp. In both species its appearance indicates that it per- 

 forms an important masticatory function in connection with the superior 

 molar. No cingula. 



Measurements. 



u. 



Leugtli of bases of M. ii and iii (No. 2) 0125 



Length of base of M. iii (No. 2) 0070 



Diameters crown M. ii (No. 1) ^ '*°t''''''P°«'«"°'' ^^ 



( transverse 0050 



Depth of ramus at M. ii (No. I) 0100 



From the Puerco Eocene of New Mexico; D. Baldwin discoverer. 

 CYNODONTOMYS Cope. 



Paleontological Bulletin, No. 34, p. 151, Feb., 1882. Proceed. Amer. Philos. Soc, 1881, p. 151 (1882). 



The characters of this genus are derived from mandibular rami. Dental 

 formula I. "? 0; C. 1 ; Pm. 3; M. 3. The premolars are counted as three, on 

 the supposition that the anterior two are one-rooted ; should it prove to be 

 singleand two-rooted, then the number will be two. The canines (orincisorsi) 

 are very large and close to the symphysis, so that there do not appear to have 

 been any other incisors. The true molars have the frequently occurring three 

 tubercles infront and a heel behind; but the arrangement is peculiar in that the 

 three tubercles are but little more elevated than the borders of the heel, and 



