FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 187 



The relative size and contour of M^ are, in fact, well within the 

 range of variation of the Torrejon species, and the teeth are not 

 significantly more transverse. The size is large for that species but 

 not beyond its presumable range and hence of doubtful significance. 

 It is impossible to give good clear diagnoses separating the two, 

 although it is my opinion that they are probably distinct. 



It is, on the other hand, probable that C. silberlingi is synonymous 

 with C monianensis (adding to the probability that it is not the same 

 as the Torrejon species). The size is about the same, and both types 

 are from one quarry. M^ is a little shorter in C. silberlingi, and some- 

 what more transverse, but these are doubtfully real, since the speci- 

 men is so poorly preserved, and if real are not marked enough to prove 

 any taxonomic distinction. M^ is definitely larger than in C. mon- 

 ianensis. The ratio of their lengths, the dimension in which they 

 differ most, is 1.10. In Torrejon specimens of the C.jerox group the 

 variation in absolute dimensions is much greater than this, and the 

 size of M^ relative to M^ or IVP also varies quite as much as the differ- 

 ence between C. silberlingi and C. monianensis, although this is a more 

 constant figure. 



The distance between P^ and the canine is almost exactly as in C. 

 monianensis. In calling it "relatively greater", Gidley must have 

 meant relative to the length of M\ but as the other tooth dimensions 

 are as great as in G. monianensis this is simply to repeat that the 

 length of A'l^ is relatively small and is not a character of the diastema. 

 M^~^ may have had larger hypocones than in C. monianensis, but this 

 is almost hypothetical, and the protocone of P* may have been stronger, 

 also rather dubious. 



I retain the name tentatively, on these very doubtful characters, 

 but beUeve that the species will probably prove to be invahd. 



CLAENODON LATIDENS (Gidley) 



Figure 41 

 f Neoclaenodon latidens Gidlet, 1919, p. 554. 



Type. — U.S.N.M. no. 8388, right lower jaw with M2-3, a small 

 fragment of Mi, and the broken lower part of the ramus from the 

 canine alveolus to the angle. Collected by Dr. J. W. Gidley. 



Horizon and localiiy. — Gidley Quarry, Fort Union, Middle Paleocene 

 horizon, Sweetgrass County, Mont. 



Diagnosis. — Gidley (1919, pp. 554-555): "Size approximately that 

 of N. monianensis, but wdth decidedly wider molars; jaw relatively 

 longer, much straighter, and more slender. Since the upper dentition 

 of A^. latidens and the lower dentition of N. silberlingi are not known, 

 these species can not now be compared, but the difference in size, 

 seems sufficient to distinguish them. 



