258 PROCEEDINGS OF THE ACADEMY OP 



On some new fossil Ungulata. Prof. Cope exhibited specimens 

 of the following ungulates, found by himself in New Mexico, while 

 acting as geologist to the United States Survey under Lieut. G. 

 M. Wheeler, U. S. E. 



Pliauchenia humphresiana, Cope, gen. et sp. nov. 



Char. gen. Represented in the collection of the expedition by 

 a left mandibular ramus which includes alveolae of all the teeth, 

 and greater or less portions of all the molars except the last, and 

 the first premolar. In the specimen the dental formula is I. ? C. 

 1; P. m. 3; M. 4; or one premolar less than in Procamelus, and 

 two more than in Auchenia. On this ground the present animal 

 is regarded as representing a new genus of Camelidse, intermedi- 

 ate between the genera named. A portion of the left maxillary 

 bone of a larger species is thought to belong to the same genus, 

 although it presents the number of premolars found in Procame- 

 lus, viz., four. The first and second are, however, very close 

 together, so as to leave about the same relative interval between 

 the first and third as is seen in the P. humphresiana, should the 

 second premolar be omitted. The latter tooth is wanting from 

 the lower jaw of the P. humphresiana. The difference in dental 

 formula between the superior and inferior dental series admitted 

 provisionally in Pliauchenia, finds justification in the formula of 

 the llamas {Auchenia), where the premolars are f. 



Char, specif. The animal now described is of about the size of 

 the Procamelus Occident alis, or somewhat larger than any of the 

 existing llamas. The mandible is stout and deep, contracting 

 rapidly forwards. The canine and first premolar are especially 

 stout, and separated by a very short diastema ; that separating 

 the first and third premolars is also short, being less than that 

 which separates the first and second in Procamelus occidentalis ; 

 could it be supposed that the second premolar is abnormally absent 

 from the P. humphresiana, the diastema would be reduced to a 

 very small compass. Without this supposition the diastemata, 

 both before and behind the first premolar, are shorter than in any 

 of the Proca.meli, as P. robustus, P. angustidens, P. heterodontus, 

 and P. gracilis. The mental foramen issues below the anterior 

 border of the first or caniniform premolar, and the anterior 

 border of the latter marks the posterior margin of the symphyseal 

 suture. The third premolar is nearly as long as, but narrower 

 than the fourth, and the true molars increase rapidly in size pos- 

 teriorly. 



3feasure??ients. m. 



Length of dental series from front of canine to front of 



last molar ... .125 



Length from canine to P. m. No. 1 .... .010 



Long diameter of first premolar 010 



Diastema to third premolar 023 



Length of third premolar ...... .011 



" " first true molar 019 



Width of crown of first true molar .... .011 

 Length of crown of second true molar 025 



