Peterson: Material Discovered in Uinta Basin. 123 



tern. The proto- and deiiteroconids are rather closeh' united and 

 have received much wear. The anterior margin of the crown has 

 developed into a crescentic ridge, which extends from the protoconid 

 forwards and inwards. The metaconid has formed a somewhat sim- 

 ihir, though less crescentic, ridge-connection with the deuteroconid. 

 This portion of the crown has also received considerable wear. The 

 tetartoconid is absent. P^ is only represented by the posterior half 

 of the crown and its detailed structure is practically a repetition of the 

 tooth in advance of it, except that the crest, which connects the meta- 

 conid with the anterior cross-crest, forms the junction with the latter 

 rather midway between the proto- and deuteroconid, instead of directly 

 with the deuteroconid as in Pj. In the paratype of Isectolophns annec- 

 tens this character is observed to be similar to that just described. 

 There is no tetartoconid, but the rise of the fold of the enamel in this 

 region of the tooth furnishes the margin of a distinct pit. The 

 cingulum is not well-developed on the premolar series. My is repre- 

 sented by the posterior portion of the crown in the type, while in the 

 paratype only the antero-external angle is preserved. The tooth 

 in both specimens has received much wear, so that its characters are 

 rather unreliable. IXW is also much worn, but it is still possible to 

 detect that the anterior cross-crest was interrupted by a longitudinal 

 valley, while the posterior cross-crest is more complete. Directly in 

 front the cingulum has formed a heavy ledge, which constitutes a 

 conspicuous addition to the base of the crown. M^- may be said to 

 have five distinct tubercles on the crown: in addition to this there is 

 again repeated the anterior ledge (parastylid) shown on M^-. There 

 are no cingula on the internal face of the molars, while externally they 

 are moderately developed. 



M EASUREMENTS. 



Type Paratype 

 No. 3045- No. 3010. 



Total length of the jaw fragment 128 mm. 



Depth of ramus at Pj 22 " 24 mm. 



Depth of ramus at M^j 31 " 31 



Length of cheek-teeth including canine 90 " 88* " 



Length of premolars 38 " 35* " 



Length of molars 45 " 45 



Antero-posterior diameter of Pf 7 " 7 



Transverse diameter of " 4 " 4 



Antero-posterior diameter of P/ 9 



Transverse " . " " 5 " 



Antero-posterior " " P3 10 " 



