CONDYLARTHEA. 489 



tubercles, two external, two median, and two internal. A strong basal cin- 

 gulum, except on inner side. Inferior true molars, besides the usual five 

 tubercles, furnished with an anterior ledge with a tubercle at its interior 

 extremity. A weak external basal cingulum. A little larger than the P. 

 vortmani. Length of superior true molars, M. .021 ; length of base of crown 

 of M. iii, .006 ; do. of M. i, .008 ; width of do., .008; length of base of crown of 

 inferior M. iii, .0085; width of do. in front, .006 ; depth of ramus at M. i, .019. 



There is some variation in the form of the smallest superior molar, 

 some being nearly round and others suboval in outline. Two mandbular 

 rami with molars represent smaller individuals. They measure as follows : 

 Length of bases of last four molars, M. .033 ; do. of true molars, .02.5 : length 

 of crown of inferior M. iii, .0082. Depth of ramus at M. ii, .<il45. 



Besides the absence of the external median tubercle, this species differs 

 from the P. vortmani in two other points. The posterior external cusp of 

 the fourth superior premolar is smaller, showing in this point also an ap- 

 proximation to the genus Protogonia. The second point is the presence of 

 the posterior intermediate tubercle on the second superior true molar. It 

 is wanting in the P. vortmani. 



The temporary fourth premolar is in both jaws a more complex tooth 

 than the corresponding permanent tooth, as usual among ungulate mam- 

 malia. The fourth superior milk molar is a little longer than wide, and the 

 anterior external cusp is compressed. In front of this the cingulum throws 

 up an angle. The internal cusps are large, and the anterior intermediate is, 

 opposite the anterior external, and anterior to the anterior internal. It 

 results that, on wearing, the anterior, internal, and intermediate, form a 

 curved surface. There are posterior and anterior cingula, but no external 

 or internal. 



The fourth inferior milk molar is extended chiefly anteriorly, where the 

 worn anterior cusp makes a crescent with the anterior external, become in 

 this tooth a median external. The interior median is opposite the exterior. 

 The heel has three cusps, two large lateral and a small median. The 

 external posterior sends a low ridge to the interior median. The second 

 and third premolars also have milk predecessors. 



Numerous specimens were found by Mr. Baldwin in the Puerco beds 

 of New Mexico. 



