50 BULLETIN 16 9, UXITED STATES NATIONAL MUSEUM 



the No. 3 beds but is not recorded in the No. 2 where there are smaller 

 and probably somewhat more primitive species of the same genus. 

 The Tetradaenodon is not distinguishable from one in the Gidley 

 Quarry, or from fragmentary specimens from high in the No. 3. The 

 1,700-foot level has cf. Conoryctes sp., fGidleyina silberlingi, Anisonchus 

 sectorius, and pantolambdids. The first and last have no apparent 

 significance for this discussion. fGidleyina silberlingi marks the first 

 (probable) appearance of that genus, which seems to be confined to 

 the No. 3 and more progressive than any tiling in the No. 2. Anison- 

 chus sectorius ranges throughout the No. 2 and far up into the No. 3. 



The 2,250 to 2,350 levels (chiefly "Princeton locahties") yield 

 Claenodon ?Jerox, Gidleyina montanensis and G. spp., Anisonchus 

 sectorius, and pantolambdids that are undetermined but are distinct 

 from anything in the No. 2 beds. Loc. 15, which is somewhere in the 

 lower No. 3 although not determined exactly as to level, yields an 

 ally of Paromomys not demonstrably distinct from the No. 2 repre- 

 sentation of that group. 



These lower No. 3 beds as a whole appear to be characterized by 

 the survival of some genera, including Claenodon, Tetradaenodon^ 

 Anisonchus, and perhaps Paromonnys and Conoryctes, and of at least 

 one species, Anisonchus sectorius, from the No. 2 beds, and by the 

 appearance of a distinctive advanced species, Claenodon fjerox, and 

 a similarly distinctive and relatively specialized genus, Gidleyina. 

 These two latter may not be real cases of faunal advance, for it is 

 possible that these animals were already present in No. 2 time despite 

 the lack of discovery, yet it seems tentatively acceptable to consider 

 them as suggestive of some slight faunal progress. The data are too 

 scanty for any definitive conclusion, but the indications are that these 

 strata have a transitional fauna between that of the No. 2 beds and 

 that of the Scarritt Quarry, about 1,000 feet above these lower No. 3 

 levels. 



The Scarritt Quarry, at about 3,350 feet, provides good data and 

 for the first time shows decisive and incontrovertible evidence of 

 faunal change in the series. Ectypodus hunteri is evidently related 

 to some species from the Gidley Quarry but is certainly distinct and 

 probably of later aspect, and the same is true of Leptacodon cf. tener. 

 Bessoecetor thomsoni also has a Gidley Quarry ally but is probably not 

 a descendant of the latter. The relative degree of specialization is 

 not clear. Elpidophorus patratus is more speciaHzed than its fore- 

 runner ?E. minor in the Silberling Quarry. Plesiadapis anceps is 

 very primitive in its genus yet is more advanced than Pronothodectes, 

 from which it could well have been derived. The relation between 

 Carpodaptes in the Scarritt Quarry and Elphidotarsius in the Gidley 

 Quarry is closely analogous to that between Plesiadapis and Pronotho- 

 dectes. Phenacolemur has no definitely recognizable ancestor in the 



