262 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 



U.S.N.M. no. 9591 is a left upper jaw with P^-M^ and about half 

 of M^, from the Gidley Quarry, which is certainly referable to Cori- 

 phagus montanus. It is deeply worn but well shows the generic 

 characters. P^ may be slightly less transverse and the external 

 cingulum of P* weaker than in C. encinensis, and all the teeth are 

 slightly smaller, but the agreement in structure is very close. 



Genus ANISONCHUS Cope, 1881 



ANISONCHUS SECTORIUS (Cope, 1881) 



Figures 77-79 



Douglass (1902b, p. 222) described and figured an Anisonchus that 

 he compared with A. sectorius but mentioned the possibility that it 

 might be distinct. The National Museum collection includes a series 

 of excellent specimens of this genus, and their pertinence to Anisorichus 

 sectorius can be rather positively estabUshed, although they may well 

 pertain to local races as will be pointed out.^^ 



Anisonchus is the only genus represented by good material in this 

 fauna that seems to be represented here by the same species as that 

 occurring in the Torrejon. It therefore is a special point of attack 

 for considering the relationships of these two widely separated Middle 

 Paleocene deposits, and the material has been subjected to detailed 

 and lengthy analysis. The results are not entirely conclusive, largely 

 owing to the small size of the available pure samples, but they nsver- 

 theless are of considerable interest, and they also provide data that 

 must be useful in future work. The full analysis would fill many 

 pages with numerical and morphological data and calculations, and 

 so it is not published here in extenso, but only such figures as are most 

 necessary to illustrate the general conclusions reached. 



A study was first made of the Torrejon specimens themselves to 

 see whether more than one species or race could be distinguished, par- 

 ticular attention being paid to possible distinction between material 

 from the two principal fossil levels of the Torrejon. The results of 

 this analysis were negative: From the data at hand it is not possible 

 to subdivide the Torrejon material, all of which is referable to Anison- 

 chus sectorius.^* Despite considerable variation, there is only one 

 specimen, Amer. Mus. no. 3533, that stands out as strongly aberrant. 

 It was collected by Baldwin in 1885, and the exact horizon and locality 

 are not recorded. Even this specimen, however, is so close to typical 

 A. sectorius that it would be methodologically incorrect to discard it 

 from the general sample. 



« Labels show that Dr. Gidley referred some of the Fort Union specimens to Anisonchus sectorius and 

 some to a new species, but he loft no diagnosis or discussion. I have carefully endeavored to visualize his 

 concept of the new species, thinking that it might correspond with one of the inconclusively indicated local 

 races, but this does not seem to be the case, and I am unable to ascertain the characters relied on by him. 



" It may be noted, however, that Matthew is incorrect in believing one of the cotypes of A. 7nandibutaTis 

 to belong to Anisonchus sectorius. Whatever the position of this very dubious species, it is not a synonym 

 of A. sectorius and probably does not belong in Anisonchus. 



