MARSUPIALIA. 733 



The first true molar is two-fifths of itself longer than the second molar, 



and viewed from above it has an oval outline, a little narrowed anteriorly, and 



with rounded extremities. Its tubercles are all truncate and closely packed 



together, so that those of the middle row have a subquadrate outline. There 



are eight tubercles in the internal row, twelve in the external, and nine in 



the median. There are no basal cingula. 1'he second and last true molar 



has a pyriform outline when viewed from above, the posterior extremity 



being the narrow one. The contraction of the outline is regular on each 



side, and the posterior extremity is rounded. There are seven tubercles in 



the external row, five in the middle row, and only two in the internal, since 



the middle row forms the internal edge of more than half the length of the 



crown. No cingula. 



Measurements. 



M. 



Length of M. i 0225 



Width of M. i at middle 0100 



Length of M. ii 0140 



Width of M. ii anteriorly 0115 



Besides the three-rowed tubercles of the first molar, and the apparent 

 absence of fourth premolars, this species differs from the Catopsalis pollux 

 in the larger size, and the larger number of tubercles in each row of the 

 molars. 



The Puerco beds of Northwestern New Mexico. D. Baldwin. 



CATOPSALIS Cope. 



Supra, page 170. 



The following additions to the characters of this genus must be made. 

 They are derived from a second species, the C. pollux, described below: 



Proximal caudal vertebra robust, the centrum rather short, and with 

 biconcave extremities. The tail was evidently stout. The distal extremity 

 of the humerus is very peculiar. There is an oval condyle on the anterior 

 side in the position of the roller, and the internal flange is not prominent. 

 The posterior trochlear groove is narrow, and its lateral borders are ele- 

 vated, so that it resembles somewhat the rotular groove of a femur. The 

 entire distal extremity resembles that of a flat femur, except that there is 

 but one tuberosity resembling a condyle, instead of two. The form ia 



