FORT UI^ION OF CRAZY MOUNTAIN FIELD, MONT. 51 



lower beds but is a progressive and specialized form. Litolestes is 

 allied to Hajdaletes and might have been, but probably was not, 

 derived from the latter (but surely not from the known species). In 

 any case, it is a distinctive genus abundant here and unknown in the 

 No. 2 beds. Tetraclaenodon occurs in both series, and the species are 

 not well enough known for useful comparison. Finally, Anisonchus 

 sectorius, which ranges throughout the No. 2, is also present here 

 (not in the Scarritt Quarry but at Loc. 18, which is not appreciably 

 different in level). 



If we discount the influence of facies and chance as far as possible, 

 it then seems clear that there is definite faunal advance from the 

 Gidley and Silberling Quarry levels to that of the Scarritt Quarry, 

 that this advance is in some cases of generic rank {Pronothodedes- 

 Plesiadapis and Elphidotarsius-Carpodaptes) but in others only 

 specific (probably in the genera Edypodus, Leptacodon, Bessoecetor, 

 Elpidophorus , and Tetradaenodon) and in part of even less degree 

 (Anisonchus sedorius)}^ 



The progressive difference in the two faunas compared is real, but 

 it is not very marked, much less than would be expected from a 

 difference in level of some 2,000 feet. As nearly as such an imperfect 

 parallel can be drawn, the difference seems to be definitely less than 

 that between the Torrejon and the Tiffany and probably not much 

 greater than between the Tiffany and Clark Fork. 



The highest faunal level, 4,350 feet, has provided Uttle good evidence 

 bearing on this discussion. Plesiadapis rex may be more progressive 

 than P. anceps but is not definitely shown to be so. The Paromomys- 

 hke form is too poorly known for useful comparison. Tetradaenodon 

 still occurs at the higher level and so probably does Gidleyina, their 

 degree of advance, if any, over comparable forms lower in the No. 3 

 beds not being clear, 



Claenodon fjerox still occurs here and seems to be quite as in the 

 lower No. 3, although the material is scanty. Thryptacodon, identi- 

 fied with much probability but not certainty, is progressive over 

 Prothryptacodon of the No. 2, but the intermediate stages in the lower 

 No. 3 are unlvnown. An ally of Haplaletes here is too poorly known 

 to give reliable evidence. Elpidophorus, probably patratus, carries 

 through from the Scarritt Quarry level. The data are too inadequate 

 to say that there is no advance over the Scarritt Quarry, or indeed 

 over the lower No. 3, but they suggest that the difference will probably 

 prove to be slight if it exists at all. 



'3 The tremendous vertical range of Anisonchus sectorius in this field, nearly 3,000 feet, is extraordinary. 

 This species and to still greater degree this genus are of unusually wide geographic range in the Paleocene, 

 the species known from New Mexico to Montana and the genus also in Louisiana, and also are unusually 

 conservative— the genus is one of the two or three that pass through from Puerco to Torrejon in New Mexico. 



