NO. I LOWER EOCENE MAMMALIAN FAUNAS — GAZIN 35 



smaller and lower crowned, with much better-developed paraconid 

 and metaconid, better-defined talonid and well-defined external cingu- 

 lum. Lower molars Tetonius-like but labial wall with a relatively 

 much shorter slope and a well-developed cingulum. Apex of trigonid 

 in lower molars transversely narrower and less compressed antero- 

 posteriorly than in Anemorhysis. 



TETONOIDES PEARCEI,s new species 

 (Plate 3, figures 3-5; plate 5, figure i) 



Type. — Right ramus of mandible with P3-M2, U.S.N.M. No. 22426. 



Horizon and locality. — Lowest beds of Knight member, Gray 

 Bull (Sand Coulee) equivalent, i\ miles south of Bitter Creek Sta- 

 tion, Sweetwater County, Wyo. 



Specific characters. — Size of teeth very close to those of "Tetonius" 

 tenuiculus Jepsen, but paraconid and metaconid of M2 and M3 dis- 

 tinctly closer together, and anterior crest from protoconid on these 

 teeth with greater anteroexternal deflection. 



Material. — In addition to the type (pi. 5, fig. i), which includes 

 the posterior premolars as well as the anterior molars, there are two 

 jaws that exhibit all three molars (U.S.N.M. No. 22382, see pi. 3, 

 fig. 4; and U.S.N.M. No. 22799), ^ j^w with only M2 but exhibiting 

 the anterior alveoh (U.S.N.M. No. 22383, see pi. 3, fig. 3), and a 

 jaw portion with P3 and P4 (Y.P.M. No. 14084, see pi. 3, fig. 5) and 

 the more forward alveoli. All of these except for No. 22799 were 

 found at the Bitter Creek locality. No. 22799 was collected by Henry 

 W. Roehler from a level 1,126 feet below the Tipton tongue on the 

 west side of the Rock Springs uplift, in association with Haplomylus. 



Among the Gray Bull materials with which comparisons were made 

 are three lower jaws that beyond doubt represent Jepsen's "Tetonius" 

 tenuiculus which I am here referring to Tetonoides. One of these, 

 A.M. No. 15066 with P4-M2 (pi. 3, fig. 6), questionably referred by 

 Matthew to "Tetonius" musculus, is, as Jepson's type, from low in 

 the Gray Bull. A specimen in the National Museum, U.S.N.M. 

 No. 19154 (pi. 3, fig. 7), with M2 and M3 from Elk Creek, also may 

 well be from low in the Gray Bull but this is uncertain. A third lower 

 jaw was recently observed in the collections at Princeton University. 

 The molars in these jaws bear a strong resemblance to those in 

 Tetonius homunculus, but with the differences noted above, and are 

 of a size to occlude well with the type upper teeth of Tetonoides 

 tenuiculus. Additional correspondence with the type of T. tenuiculus 



s Named for Franklin L. Pearce who aided me on so many field expeditions. 



