NO. I LOWER EOCENE MAMMALIAN FAUNAS GAZIN 29 



Specific characters. — Much smaller than Pelycodus? tutus Cope, 

 but resembles it in most of the following: Lower molars elongated. 

 Trigonid decidedly narrow with paraconid well separated from meta- 

 conid in both Mi and M2. Talonid basin broad, deep, and compara- 

 tively smooth. Posterior crest from hypoconid swings down to 

 cingulum posterointernally and is separated from the entoconid by 

 a deep notch. Entoconid high, relatively conical and forward in 

 position. It joins the metaconid by a high, laterally flexed crest. 



Material. — In addition to the type (pi. 4, fig. 4) there is a portion 

 of the left ramus of a mandible with P2-P4 (Y.P.M. No. 14697; 

 pi. 4, fig. 2) and a jaw fragment with M3 (Y.P.M. No. 14698; pi. 4, 

 fig. 3), probably not of the same individual, in Marsh's collection 

 from the Bitter Creek locality. An isolated lower molar, evidently 

 M2, from the Red Desert locality east of Steamboat Mountain, also 

 belongs to this form. 



Discussion. — The characters of the lower molars, first noted by 

 Cope (1877, p. 141) and later by Matthew (1915c, p. 441) for 

 Pelycodus tutus, and here observed in P.? praetutus, are so very 

 distinctive in comparison with Gray Bull, Lysite, and other San Jose 

 and lower Knight material that there might seem justification in 

 recognizing a distinct genus, were it not for the striking variability 

 of these features in later Notharctus. While the paraconid seems 

 progressively lowered or reduced in much of the material of No- 

 tharctus, the talonid largely retains the form seen in Pelycodus 

 trigonodus but with the greater isolation of the entoconid from the 

 posterior crest, particularly in M2, approaching, although not quite 

 reaching, the condition seen in P.f tutus and P.f praetutus as an 

 extreme. Nevertheless, typical Pelycodus apparently exhibits greater 

 stability in these features and the P.f praetutus-P .f tutus line seems 

 rather distinctive in comparison with contemporaries. 



NOTHARCTUS LIMOSUS Gazin 



(Plate 4, figure 5) 



Several additional jaws, maxillae, and isolated teeth belonging to 

 Notharctus limosus have been obtained from Knight exposures be- 

 neath the Fontenelle tongue in the vicinity of Big Piney and La 

 Barge. These do not, however, yield any new information beyond 

 that covered in the earlier report. 



A maxilla (P.U. No. 161 23) with M^-M^ collected by Morris 

 from Knight beds beneath the Tipton tongue near Dad, Wyo., re- 

 sembles N. limosus in general form and in the relative width (trans- 



