CHAPTER II 



SYSTEMATIC POSITION OF NEOTOMA AND ITS 

 SUBGENERA 



Under current usage the genus Neotoma, as segregated by- 

 Say and Ord in 1825, is one of the six genera included in the 

 subfamily Neotominae, of the family Cricetidae. Perhaps 

 the majority of authorities consider this subfamily to be most 

 nearly related to the subfamily Microtinae, chiefly because 

 of the enamel pattern of the molariform teeth. This is a 

 rather logical contention, but on the other hand, it is not 

 unlikely that the tooth pattern is fortuitous in this respect, 

 having been brought about by certain food habits, and that 

 the similarity of the pattern in the two subfamilies is not of 

 great phylogenetic significance. 



The generic diagnosis as given by Goldman (1910) is as 

 follows: ''Molar crowns flat; first and second upper molars 

 with middle enamel loops undivided; third lower molar with 

 two transverse enamel loops (not S-shaped as in all other 

 genera of the subfamily) ; bullae obhque, tapering anteriorly.'^ 



The subgenus Teonoma was proposed by Gray in 1843, 

 and Homodontomys by Goldman in 1910. 



The key to the three subgenera, as given by Goldman, 

 is as follows: 



a. Tail terete, not bushy. 



b. Maxillary tooth row much narrower posteriorly than an- 

 teriorly; middle lobe of last upper molar not divided 



by inner reentrant angle Neotoma 



h'. Maxillary tooth row slightly narrower posteriorly than an- 

 teriorly; middle lobe of last upper molar partially or com- 

 pletely divided by inner reentrant angle Homodontomys 



a'. Tail flattened and bushy Teonoma 



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