520 THE MAMMALIA OF THE UINTA FORMATION. 



ISECTOLOPHUS ANInECTESTS. 

 Plate X. 



This genus is represented in the Princeton collection by portions of four individ- 

 uals, which apparently belong to the same species, and by the type of a second species 

 from the Bridger. The type specimen (]N^o. 10,400) consists of the second premolar and 

 first and second molars of the maxillary series and the last lower molar and portions 

 of the last premolar and first molar of the mandibular series. The second specimen 

 (No. 10,401) preserves the first upper molar and fragments of the premolars and the 

 fourth lower premolar associated with a portion of the ramus ; also a complete car- 

 pus and portions of the metacarpus ; also the cuboid and metatarsal elements, in 

 addition to the vertebral and limb fragments. The third specimen (iSTo. 10,393) is a 

 mandibular fragment containing the fourth premolar and first and second molars. 



Dentition. 



Molars. In the type specimen (Wo. 10,400) m. ^ and m. '' are preserved of the 

 superior series. The external face is continuous but strongly ti'ilobate (Fig. la) with 

 a pronounced external cingulum and prominent anterior accessory cusp. The third 

 lobe of m. - is strongly produced beyond the junction of the posterior crest (Fig. 1). 

 The transverse crests are rather low and obtuse, curving oblicpiely backwards. At 

 the head of the main valley, directly opposite the median external lobe, is a low but- 

 tress. The inteiuial cingulum is prominent, extending upon the anterior and poste- 

 rior faces of the crown. The first molar is a smaller tooth of very similar pattern. 



The third lower molar (Fig. 2) has a prominent creseentic heel. The anterior 

 crests are stout and slightly oblique ; the outer face shows a creseentic prolongation 

 inwards, which is rather faint in the middle crest but is strongly produced in the an- 

 terior crest, the crescent thus formed being strengthened by a buttress. This 

 buttress is a marked feature of the first and second lower molars, as seen in another 

 individual (No. 10,391)). In the latter the crowns are unworn (Fig. 11), the crests 

 are subcrescentic ; the buttress is very distinct in the concavity of the anterior crest 

 and this crest extends inwards, forming an anterior valley. 



Premolars. With the tyjje specimen there is a superior premolar (Fig. 1) in 

 which the internal lobe is single, with a slightly paired crest extending to the outer 

 lobes. This tooth is almost unquestionably the second })remolar. Associated with 

 the third specimen also there are portions of the external lobes probably belonging 

 to pm. '". 



The fourth inferior premolar is preserved in each specimen (Figs. 2 and 11). 



