21 



aloue; the latter on that of the lower ja^Y. lu the present species we 

 have the two kinds of teeth combined. The relations are, however, 

 quite different from those found in the P. rohustus and the P. angusti- 

 dens. As to the reference of H. caninus to the former rather than the 

 latter of these two, it depends on their coincidence in the transverse 

 Avidth of the premolar teeth, and is rendered probable by the fact that 

 they are from the same horizon and approximate locality. 



In the superior and inferior dentition of P. heterodontus, it is to be 

 noticed that the first premolar is situated well anteiiorly, the space 

 separating it from the second premolar being twice as long as that be- 

 tween it and the canine. In P. rohustus these interspaces are equal, (in 

 the lower jaw,) as in P. aiKjustidens. In the present camel the 

 third incisor is separated from the canine, in the lower jaw, by a 

 space nearly equal to that between the canine and first i)remolar; 

 in P. angustidens (and i^robably P. rohustus and JI. caninus) this 

 space is very much less, and just sufficient to admit the superior canini- 

 form incisor. In the i)resent species the lower border of the symphysis 

 is below the canine, and hence the symphysis is much shorter than in 

 P. angustidens^ as it is steeper and concave on the anteroinferior face. 

 It is not co-ossified in the specimen, while it is so in the P. angustidens. 

 On each side of the suture below is a small compressed descending 

 tuberosity. The mental foramen Is below the first premolar. The 

 second and third lower premolars are two-rooted and compressed ; the 

 third presents an angle inward at its anterior end. 



The premaxillary bones are attenuated and simple in front, with little 

 indication of contact or connection across the middle line. The side of 

 the muzzle is concave above the first premolar. Last incisor vertical in 

 direction. 



The maxillary teeth associated with the above-described premaxillary 

 bones represent the entire series except the second and third premolars. 

 These present strong exterior ribs between the columns, and weak ones 

 between, on the third molar. These teeth present no extra lobes, tuber- 

 cles, nor columns, and the cement deposit in the lakes is very small. 

 The r. M. ,'3 and M. 1 are each about as broad as long. 



Measurements of uppvrjaic. 



M. 



Length true molars , 0.083 



Length last molars, (outside) 036 



Width last molars, (^anterior column) , . . .016 



Length of first molar 020 



Width of first molar 019 



Length of last premolar 014 



Width of last premolar 013 



Length from P. M. 1 to canine 016 



Langth from P. M. 1 to I. 3 , .036 



Lsngth from I. 3 to end of premaxillary 038 



Measurements of lower jaw. 



Length from apex I. 3 to end P. M. 3 .120 



Length from apex I. 3 to P. M. 2 098 



Length from apex I. 3 to P. M. 1 052 



Length from apex I. 3 to canine 025 



Depth at P. M. 3 010 



Depth at canine 041 



From the heads of Pawnee Creek, Colorado. 



