142 ^fr. 0. Tliomas on the Grouping of 



8kull ill gcncial form like that of P/ii/Uotis, but the supra- 

 orbital edi^os riilgcil and divergent as in tiie larger species of 

 Ilesperomys. Anterior edge of zygomatic plate undercut, 

 concave. Bullae generally large. 



Type. Graomys griseo-flavus {^}[us gr{seo-jlavus,W&i&x\\.). 



Other members of the genus : — 



Graomys chacoensis, All. (described as Pliyllotis chacoensis) . 



„ cachinus, All. (^Pliyllotis cachinus). 



,, domorum, Thos. (Eligmodoiitia domorum). 



,, griseojlavus centralis^ Thos. (C. g. centralis) . 



Phyllotis, Waterh., 1837. 



Size various. Form slender, graceful. Ears long. Tail 

 about as long as or (generally) longer than head and body, 

 thinly haired, not pencilled. Feet normal, slender, with the 

 usual j)ads small and well defined. Mamnire 2 — 2=iS. 



Skull, compared with that of the Euneomys group, long 

 and narrow, the zygomata not widely expanded. Interorbital 

 region more or less parallel-sided, its edges, at least in the 

 larger forms, not broadly divergent ])osteriorly and not 

 ridged. Anterior edge of zygomatic plate straight or occa- 

 sionally slightly concave, but never distinctly undercut. 

 Bullffi generally small, though larger than in Ilesperoinys. 



Teeth brachyodont. 



Type. Fhyllotis darwini {Mas darwini, Waterh.). 



About a score of other species appear rightly referable to 

 Fhyllotis. 



Euneomys, Coues, 1874. 



Size various. Form comparatively stout, more or less 

 Microtine. Tail medium or short, well-haired, especially at 

 tip. Feet stout, dumpy, generally heavily fringed; pads 

 large, low, more or less tilling up the surface of the palms 

 and soles. Mammae 2 — 2 = 8. 



Skull comparatively short, stout, rounded, the zygomata 

 widely expanded. 



Incisors grooved or smooth. Molars more bypsodont than 

 in Fhyllotis and the otlier allied genera. 



Type. Euneomys chinchilloides {Reithrodon chinchilloidesy 

 Waterh.). 



Three subgenera, as follows : — 



Euneomys, s. s. 



Tail of medium length. Palms and soles completely 

 naked. 



