FORT UNIOX OF CRAZY MOUNTAIN FIELD, MONT. 



155 



progressive than in P. maturus, being to some extent intermediate in 

 structure between P3 and P4 of that species. The supposed depression 

 of the molar trigonids, stressed by Gidley, involves slight differences 

 that defy accurate measurement. To my eye they do not appear at 

 all less elevated than in P. maturus. The trigonids of M2_3 are rela- 

 tively slightly shorter, and the paraconids may be still more nearly 

 connate with the metaconids. More definite is the fact that on M2 the 

 trigonid is nearly as wide as the talonid, while in P. maturus it is 

 definitely narrower. Perhaps in keeping with the smaller size, the 

 heel of M3 is rather simple, and although it has the basic structure of 

 P. maturus in some variants the third lobe is less wide and its two main 

 cusps less distinct. 



The available upper teeth of this species are all deeply worn, and I 

 believe that the characters given by Gidley, "cusps and lophs depressed 

 and basins shallow; protoconules present but less well defined than 

 P. maturus; metaconules absent", are all due to this wear, or at least 

 that the wear makes it impossible to know whether these are true 

 morphological characters or not. P* is much less transverse than in 

 P. maturus, and the inner sides of the bases of M^~^ are less strongly 

 bilobed. Otherwise the structure seems to be very similar, as far as it 

 can be surely determined. 



The species is decisively distinct from the genotype, and there can 

 be no question as to its validity in spite of the fact that P. maturus and 

 P. depressidens were absolutely contemporaneous and both are known 

 only from the same very limited locality. These facts and the very 



Table 32. — Measurements of known specimens of Paromomys depressidens 



Lower Jaws 



Upper Jaws 



