48 



PROCEEDINGS OF THE NATIONAL MUSEUM 



molars more nearly trian^lar in occlusal view. Taloiiid basin of 

 lower molars slightly less constricted anteriorly. 



Description. — Anisonchus is represented in the Wagonroad collec- 

 tion by a maxillary portion and a lower jaw fragment found to- 

 gether and both having the first two molars preserved, U.S.N.M. 

 No. 16192 (fig. 27), which has been made the type of Anisoiwhus 

 oligistus. Six other specimens are referred to this species. These 

 include two maxillary fragments, with M^-M^ and P*-M^ somewhat 

 damaged, two lower jaw fragments each with the greater portions 

 of two molars, and two isolated premolars. 



Anisonchus oligistus is apparently the smallest species known 

 of this genus, having both upper and lower molar teeth a little 

 smaller and relatively narrower transversely than in material of A. 

 gilliamis from the Puerco. The lower teeth are also smaller and 

 more slender than in the type of Anisonchits onostus from the Dragon 

 level. 



The upper molars appear for the most part very much like those 

 in other species of Anisonchiis, but are somewhat more nearly trian- 

 gular in outline, as viewed from below, with the lingual portion a 

 little more constricted anteroposteriorly and the hypocone column 

 distinctly lingual, though not so markedly lingual as in HaplocomLs. 

 The anterior cingulum extends to a markedly lingual point but does 

 not exhibit a distinct protostyle. 



The lower molars in addition to their slenderness show relatively 

 high trigonids, and the cusps appear to be more acute than in 

 A. gillianus. Moreover, the paraconid may be slightly more external 

 in position. The talonid appears deeply basined in the type, and 

 the crest extending forward from the hypoconid joins the posterior 

 wall of the trigonid at a position which appears to be slightly more 

 external. This is not so obvious in the type, but noticeable in the 

 two referred lower jaws. As a result the talonid basin in the 

 referred specimens appears somewhat less constricted anteriorly. 



Table 11. — Measurements (in millimeters) of upper and lower teeth of 

 Anisonchus oligistus (U.S.N.M. No. 16192) 



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

 lingually and at right ;ingles to the direction of the tooth row. 



