2 lO Bulletin American Museum of Natural History. [Vol. XVI, 



The eight specimens from the Wind River formation (Amer. 

 Mus. Nos. 4743-4748 inclusive) , referred by Cope (Tertiary Ver- 

 tebrata, p. 217) to M. elegans Marsh (or 

 g]^^^p^^ M. gracilis Leidy ) , represent a larger animal 



_ J/_ffl>_m:3 than C. latidens of the Wasatch ; and agree 



■^ jSiafWiliklL closely with M. scottianus in size of the 

 /t;^'---'"'"^/ teeth, but certain of them differ in the 

 ^^^^^^^^ greater depth of the mandible and coal- 



Fig 37 '^Mzcros:y- csccncc of thc fangs of pg (see No. 4743)- 

 fm^^^Mut'copeT'No-. (Sp. 44) "Microsyops" speirianus (Fig. 



ramus.^°"'°" ''^ "^^' 37)- Thc typc Certainly does not belong 

 to this genus. It resembles Anaptomorphus 

 slightly. 



4. Bridger (Bartonien) Stage. 



(Sp. 8) Microsyops gracilis. — Leidy's type of the genus 

 (Microsyops gracilis of the Bridger) was a small lower jaw in 

 which he mistook the homologies and erroneously described 

 six molars (ms. and pms.) and enlarged "canines," remarking 

 that the number of incisors was indeterminate. Unlike those 

 of the Anaptomorphidas the lower molars are readily recog- 

 nized by the narrow trigonid, now depressed to the level of the 

 talonid, i. e., more bunodont, depressed paraconid, behind 

 which is the broad talonid bearing a hypoconulid; nig has a 

 small cuspidate hypoconulid, unlike that in the Notharctidae. 

 So far as reported, upper molars have not been found as- 

 sociated, but it is probable that they are rightly identified 

 in the broadly triangular (as distinguished from the more 

 transversely oval form of the molars in the Anaptomorphidae 

 and the more quadrate form in the Hyopsodontidae) tri- 

 tubercular teeth, with a small cingule representing the hypo- 

 cone, with intermediate spaces on the palatal side, as in all 

 forms in which the trigonid is present ; rudimentary conules 

 and para-, meso-, and metastyles; the type of Palceacodon 

 verus Leidy, described immediately after that of Microsyops, 

 is such a tooth with small conules and a rudimentary hypo- 

 cone (Leidy, '73, pi. vi, fig. 46). 



