NO. I LOWER EOCENE MAMMALIAN FAUNAS — GAZIN 75 



about 20.0 mm. The approximately lo specimens from the New Fork 

 are mostly isolated teeth of large size. 



Hyracotherium craspedotum is evidently a contemporary of H. 

 vasacciense but probably derived from earlier H. augustidens. H. 

 vasa€ciense, however, may have originated in a somewhat more pro- 

 gressive form than typical H. augustidens, such as represented by the 

 material from Bitter Creek. H. craspedotum most likely did not give 

 rise to Orohippus. 



BRONTOTHERIIDAE 



LAMBDOTHERIUM POPOAGICUM Cope 



(Plate 12, figures 8 and g) 



In the later collecting at the La Barge and New Fork levels, 

 remains of Lambdotherium continued to be among the most fre- 

 quently encountered. With the exception of a well-preserved pair 

 of lower jaws (U.S.N.M. No. 22758) from the Muddy Creek locality 

 12 miles north of Big Piney, near where the earlier-described (1952, 

 pi. 10) skull was found in 1949, much of the material consists of 

 rather fragmentary jaws and isolated teeth. Some 30 or more speci- 

 mens were added to the La Barge collection and something over 70 

 were found in the New Fork beds, which have received rather more 

 attention in late years. 



No material of Lambdotherium has as yet been encountered in the- 

 rather sparsely fossiliferous Cathedral Bluffs beds in the Washakie 

 Basin ; however, at least 21 specimens referred to L. popoagicum have 

 been seen in collections representing the Dad faunule from beneath 

 the Tipton tongue in the same area. These are for the most part 

 isolated teeth in the collections of Princeton University and the Uni- 

 versity of California, although in the Princeton collection there is a 

 lower jaw (P.U. No. 161 18) with three molars. A single specimen 

 in the National Museum collection (No. 22759) exhibits P4 and Mi. 



BRONTOTHERIID, near PALAEOSYOPS FONTINALIS Cope 



The Princeton University specimen (No. 161 10) from the Cathe- 

 dral Bluffs that Morris (1954) and I (1959) have listed as Eotitanops, 

 sp., is a right maxillary fragment with Dp^ Dp* and M^ Comparison 

 of the teeth with those in the type of Palaeosyops fontinalis (A.M. 

 No. 5107) shows them to be quite similar and only slightly smaller. 

 The length of the ectoloph portion of M\ for example, measures 

 24.0 mm., whereas in the type this dimension is 26.2 mm. Also, M^ 



