NO. I LOWER EOCENE MAMMALIAN FAUNAS GAZIN 8l 



M2-M3, from the Gray Bull horizon of the Knight west of Elk Moun- 

 tain in the Fossil Basin represent Diacodexis, and may well be of the 

 common Wasatchian form of the Bighorn Basin, Diacodexis met- 

 siacus. An M3 in one jaw portion (U.S.N.M. No. 22242) would 

 appear to be large for this species, but it is not as large as that indi- 

 cated by Sinclair (1914, p. 293) for Diacodexis robtistus. Reasons 

 for regarding D. metsiacus distinct from D. chacensis were previously 

 (Gazin, 1952, p. 71) stated. 



Isolated teeth from the Gray Bull levels at Bitter Creek Station and 

 in the Red Desert east of Steamboat Mountain may also represent this 

 species, as well as a last lower molar from the Wasatchian of uncertain 

 level just to the north of Tipton Butte. 



The two jaws from the type Knight near Knight Station, cited by 

 Van Houten (1945, p. 458 ; see also Gazin, 1952, p. y2) as Diacodexis, 

 sp., have since been located in the American Museum collections and 

 found to be of Hexacodus. 



DIACODEXIS, near D. SECANS (Cope) 



A second specimen in the La Barge fauna representing a species 

 of Diacodexis that appears to be somewhat larger than D. metsiacus 

 was found to the west of Big Piney by N. P. Privrasky of the U. S. 

 Geological Survey near the area mapped as Almy by Schultz ( 1914) . 

 The jaw (U.S.N.M. No. 22243) contains only the last lower molar, 

 which is slightly larger than that in No. 192 18 from 12 miles north 

 of Big Piney. An upper molar (U. of C. No. 43885) from near Dad, 

 however, seems relatively small for this species. Possibly this should 

 have been referred to D. metsiacus, but, in the absence of information 

 concerning range in size of teeth of D. secans, it is tentatively included 

 here because of the horizon represented. An incomplete M3 in the 

 New Fork collections may also be included with these as possibly 

 representing Diacodexis secans. 



DIACODEXIS, cf. ROBUSTUS Sinclair 



Some jaw fragments and teeth, including an upper and two lower 

 molars of a large form of Diacodexis were found by McKenna's 

 party near Dad, Wyo. The specimens have the University of Cali- 

 fornia number 46707 but evidently they do not all come from the same 

 individual. The teeth are of a size comparable to those from the 

 Gray Bull described by Sinclair (1914) as Diacodexis robustus. The 

 relative width of Mi, however, might suggest a closer relationship to 

 much smaller Diacodexis olseni, which is a Lost Cabin species. A 



