PALEOCENE MAMMALS OF CENTRAL UTAH — GAZIN 



45 



conid has become distinct from the prot^conid caimot be exactly 

 determined, owing to wear, but it is clearly not separated to the ex- 

 tent seen in P. ca)inidens. 



The lower molars are wider than in the Carsioptyckus material at 

 hand but not so wide as is common in Torrejon material of Peiipty- 

 chus. These teeth show a slight cingulum around the external side, 

 which was not observed in material of the other forms. The small 

 seventh cusp located about in the center of the crown of the lower 

 molars of Perlpfychus carinidens is not present in the first two molars 

 of P. gilmorei but is weakly developed in M3. This cusp is not known 

 in Carsioptychus. 



Table 9. — Meaiiurements {in millimeters) of upper teeth (U.S.N.M. No. 155S7, 

 type) and lower teeth {U.S.N.M. No. 15689) of Periptychus gilmorei 



' The transverse diameter of the upper teeth is taken from the external cingulum to the base of the enamel 

 lingrually and at right angles to the direction of tooth row. 



Genus ANISONCHUS Cope 



ANISONCHUS DRACUS« Gazin 



Anisonchus dracus Gazin, 1939b, p. 278. 



The larger of the two species of Anisonchus is represented in 

 the Dragon collection by three maxillary portions with one to four 

 teeth apiece and five lower jaw fragments with one or two molars 

 each. The type, No. 15745, is a maxillary fragment with P* to M' 

 preserved (fig. 25). 



The upper teeth in No. 15745 are clearly of an Anisonchus type 

 and are intermediate in observed characters between A. gillianus 

 and A. sectorius of the Puerco and Torrejon, respectively; com- 

 parable in this respect to Periptychus gilmorei in its relationship 

 to the two developmental stages occurring in the San Juan Basin, 

 noticeably in the relation of the length to the width of the tooth 

 crowns. 



The Dragon form approaches A. sectorius in size but retains rela- 

 tively wider teeth transversely, and longitudinally a little shorter, 

 and the cusp pattern is not so restricted transversely. The upper 

 teeth appear also to have a longer, more gradually sloping lingual 

 wall, with a somewhat more lingually placed hypocone column. The 



t-^ipoKusv, dragon, from Dragon Canyon. 



