48 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 



Table 3. — Combined faunal list, Crazy Mountain Field, Mont. — Continued 



FAUNAL SUCCESSION 



The No. 1 beds have yielded only fPtilodus sinclairi from near the 

 base; Claenodon vecordensis, Chriacus pugnax, fMimotricentes sp., and 

 Tetraclaenodon fsymbolicus from near the middle part; and Mimotri- 

 centes angustidens from the top. The first and last of these forms are 

 inseparable from species occurring well up into the No. 2, and so is 

 Tetraclaenodon fsymhoUcus. Claenodon vecordensis and Chriacus 

 pugnax are distinct species but cannot be considered to be clearly 

 ancestral to anything known from the No. 2. The evidence is inade- 

 quate to demonstrate either occurrence or absence of distinct faunal 

 advance within the No. 1-No. 2 series. It does suggest, however, 

 that such advance must have been relatively slight and that it was 

 probably of less than generic rank, if it occm'rcd. The data definitely, 

 if not altogether conclusively, oppose the hypothesis that the difference 

 between No. 1 and No. 2 faunas can have been as great as between 

 Puerco and Torre j on. 



Within the No. 2 beds the first important point is that the Gidley 

 and Silberling Quarry faunas are identical in degree of evolutionary 

 progress and show no significant difference in age despite a small 

 difference in level, about 65 feet. There are 23 species definitely- 

 identified in the Silberling Quarry. Seventeen of these also occur in 

 the Gidley Quarry and, as shown in the systematic descriptions, these 

 suggest no difference, even of less than specific rank, between the 

 forms in the two quarries. Four Silberling Quarry species do not 

 occur in the Gidley Quarry but do occur at lower levels, so that their 



