488 THE PUEECO EPOCH. 



cingula. The principal peculiarity of the lower dentition of this species 



and the one from which it is named, is the form of the third or fourth 



(probably third) premolars, both of which are preserved. They have a 



compressed apex, which descends steeply to the anterior base, without basal 



or lateral tubercle. The base of the crown spreads out laterally behind, 



and is broadly rounded at the posterior margin, so as to resemble the toe 



of a wide and moccasined foot. It is depressed, the surface rising to the 



apex from a flat base. 



Measurements. 



Diameters of second superior molar )'*°t''r°P''*t«"'"" 0080 



( transverse 0100 



Diameters oflast superior molar ^ '*"**"■"?"«*«"<"■ 0067 



I transverse 0085 



Length of inferior true molars 0258 



Diameters of M.ii^'*°*^'""P°^*<^"*'^ 009 



( transverse 008 



DiametersofM.iii^^"**™?''^*^"""' 0086 



( transverse 0068 



Diameters ofthePm.iii I ''"t'^'^^Po^t'^"'"- 008 



( transverse 005 



About the size of the P. puercensis. 



Phenacodus puercensis Cope. 



Proceeds. Amer. Philoa. Soc, 1881, p. 492. Paleontological Bulletin No. 33, p. 492, Sept. 30, 1881. 

 Plate XXV e; figs. 12-13. LVII/; figs. 8-9. 



In the Paleontological Bulletin No. 34 I combined this species with 

 the P. vortmani, which it greatly resembles in size and proportions. It is 

 an abundant species in the Puerco formation of New Mexico, and I have 

 recently secured numerous jaws with teeth. Among these there are six 

 fragments of maxillary bones with molars. I find, on comparing these with 

 the true P. vortmani of the Wasatch beds, that they uniformly differ in the 

 absence of the external tubercle which rises from the cingulum opposite 

 the space between the principal external cusps. In this respect they re- 

 semble the Protogonia subquadrata. The difference is important, and I an- 

 ticipate that other characters will be found confirmatory of the distinction 

 of the species here maintained. 



Typical specimens have the following characters: 



Last superior molar smallest; first and second true molars with six 



