Cope.1 1^ [May 16, 



figures similar specimens from various parts of the Eastern and Southern 

 States. 



Equus crenidens Cope, sp. nov. 



This large species of true horse is represented by molar teeth and frag- 

 ments of jaws belonging to two individuals preserved in the Museo Na- 

 cional of Mexico, and to two others preserved in the Escuela des Minas- 

 The typical specimen includes the three premolars of the upper jaw of an 

 adult in perfect preservation. 



The species is primarily distinguished by the close and strong wrinkling 

 of the enamel border of the lakes of the superior molar teeth. This 

 wrinkling, or vertical plication, reminds one of what is seen in the Ele- 

 2)7ias indicus. This wrinkling is not found in the enamel edges which 

 border the interior crescents on the inner side, nor in those bordering the 

 internal lobes or columns. The borders of the lakes are not folded in the 

 complex loops seen in Equus major Dek., but have the plainer looping 

 seen in the Equus tau Ow. The grinding faces are nearly square. That 

 of the second premolar is a rather shortened triangle, and less produced 

 anteriorly than in the E. tau. The crowns of the third and fourth pre- 

 molars are long and slightly curved. 



The measurements show that this is one of the larger species of horse. 

 Measurements. M. 



Diameters of P-m. ii / anteroposterior 0430 



i transverse 0305 



Diameters of P-m. iii \ anteroposterior 0335 



t transverse 0340 



Diameters of P-m. iv j anteroposterior 0310 



<- transverse 0350 



The crimping of the enamel of the lakes distinguishes this species from 

 the others of the genus. 

 From Tequixquiac. 



Equus tau Owen. Philosophical Transactions of the Royal Society, 

 1869 ; p. 565 ; pi. lxi ; fig. 4. 



Of this species there are preserved in the Museum Nacional five superior 

 molars, some of which belong apparently to one individual. In the Escuela 

 des Minas, the series is a fine one. There are two skulls lacking the occi- 

 put ; one skull lacking the occiput and muzzle ; parts of both maxillary 

 bones with teeth, of one skull ; and a single maxillary bone with teeth, of 

 a fifth skull. The specimen mentioned under the second head, has teeth 

 and palate preserved, as in the figure given by Owen of his Equus conver- 

 sidens, and I suspect it was from this specimen that the photograph was 

 taken from which Professor Owen's figure and plate were made. It is pos- 

 sible that his figure and description of the Equus tau were made from one of 

 the maxillary bones mentioned under head three. I am not able to perceive 

 the specific differences between these specimens. The character displayed 



