New Mice from Mexico and Guatemala. 117 



eves, and along middle of back ; under parts white, the plumbeous basal 

 fur showing through; wrists, ankles, and tail dusky; fore feet white ; 

 hind feet whitish strongly clouded with dusky. 



Cranial characters. — Skull like that of thomasi, but less massive, lacking 

 the supraorbital ridges, and with the posterior reentrant angle on inner 

 side of irij less pronounced. In thomasi the supraorbital ridges slightly 

 overhang the orbits so that they intercept the dividers in taking the in- 

 terorbital breadth ; in nelsoni the upper surface of the frontal interor- 

 bitally is so much narrower that in taking this measurement the dividers 

 rest on the vertical plane of the orbit about 2 mm. below the top of the 

 frontal. 



Measurements. — Type specimen: Total length 302; tail vertebra 172; 

 hind foot 35. Average of 2 specimens from type locality : Total length 



Peroniyscus zarhynchus sp. now 



Type from Tumbala, Chiapas, Mexico. No. 76119, $ ad., U. S. Nat. 

 Mus., Biological Survey Coll. Collected Oct. 20, 1895, by E. W. Nelson 

 and E. A. Goldman. Orig. No. 8606. 



CharacU rs. — size very large ; ears large and nearly naked ; tail very long 

 and appearing naked ; hind feet long and slender; coloration dark. 



Color. — Upper parts dusky, becoming seal brown on sides (sometimes 

 chestnut fulvous on flanks); under parts whitish, the plumbeous basal 

 fur showing through ; pectoral region strongly washed with chestnut, the 

 chestnut suffusion sometimes spreading over belly ; tail (skin) dusky- 

 above, yellowish white below ; fore and hind feet whitish, the latter 

 slightly clouded. 



Cranial characters. — Skull very large and long with exceedingly elongated 

 rostrum ; small audital bulla' ; weak and slender zygomata ; zygomata nar- 

 row anteriorly, and only slightly notched by anteorbital slit, which is 

 drawn out on side of rostrum as in Megadontomys. The skull resembles 

 that of Megadontomys nelsoni in size and general appearance, but is dis- 

 tinguishable by the much greater length of rostrum and incisive foramina, 

 narrower interparietal, less flaring nasals, and much smaller molar teeth. 

 It does not require close comparison with any known species. 



Measurements. — Type specimen: Total length 324; tail vertebrae 176; 

 hind foot 35. Average of 13 specimens from type locality: Total length 

 314 ; tail vertebrae 169 ; hind foot 35.4. 



Peromyscus zarhynchus cristobalensis subsp. now 



Type from San Cristobal, Chiapas, Mexico. No. 76109, 9 ad., U. S. 

 Nat. Mus., Biological Survey Coll. Collected Oct. 2, 1895, by E. W. Nel- 

 son and E. A. Goldman. Orig. No. 8536. 



Characters. — Similar to r. zarhynchus from Tumbala, but paler and more 

 fulvous, with slightly smaller skull. 



Color. — Upper parts dusky brown, becoming dusky on nose, around 

 eyes, and along middle of back and everywhere mixed with fulvous tipped 



