22 Proceedings of the Biological Society of Washington. 



Remarks. — Sigmodon hispidus confirms appears to be a well-marked 

 form restricted in distribution to the upper part of the Gila River Valley. 

 Its general characters indicate as close relationship to S. h. berlandieri of 

 the Rio Grande Valley as to its geographic neighbors in Arizona. In size 

 it departs most widely from S. h. arizonae, which is a much larger animal 

 confined to the upper part of the Verde River Valley. 



Specimens examined. — Fourteen, all from the type locality. 



Sigmodon hispidus jacksoni, subsp. nov. 



JACKSON'S COTTON RAT. 



Type from 3 miles north of Fort Whipple (near Prescott), Arizona 

 (altitude 5,000 feet). No. 214121, c? subadult (third upper molar slightly 

 worn), U. S. National Museum (Biological Survey Collection), collected 

 by H. H. T. Jackson, July 8, 1916. Original number 456. 



Geographic distribution. — Known only from the plateau region near 

 Prescott, Arizona. 



General characters. — A pallid form, similar to Sigmodon hispidus ere- 

 micus in general color, but upperparts more uniform, the sides not so 

 distinctly lighter than back as in that subspecies; skull differing in detail, 

 especially the greater breadth of braincase. Contrasting with Sigmodon 

 hispidus arizonae in smaller size, paler color and cranial features. 



Color. — Type: Upperparts near light ochraceous-buff (Ridgway, 1912), 

 finely and nearly uniformly mixed or lined with dusky, the sides scarcely 

 paler than back ; underparts and feet dull whitish or grayish ; ears pale 

 buffy inside; tail brownish above, grayish below. 



Skull. — Closely resembling that of S. h. eremicus, but braincase broader; 

 audital bullae more inflated; interparietal small, much as in eremicus. 

 Compared with that of S. h. arizonae the skull is smaller; frontal region 

 shorter, and lacking the narrow posterior prolongation on median line 

 between parietals present in arizonae; interparietal and audital bullae 

 relatively smaller. 



Measurements. — Type: Total length, 249; tail vertebrae, 108; hind 

 foot, 33. Skull: Greatest length, 31.2; zygomatic breadth, 18.2; inter- 

 orbital breadth, 5 ; nasals, 11.4 ; width of braincase (in front of descend- 

 ing process of supraoccipital), 13.5; maxillary toothrow, 6.4. 



Remarks. — This subspecies is based on a single immature specimen 

 which differs so markedly from the considerable series of comparable 

 examples now available of neighboring forms as to warrant recognition. 

 The type locality is only a few miles from that of S. h. arizonae, but at 

 a higher elevation and in a different life zone. 



Specimens examined. — One, the type. 



Perognathus intermedius phasma, subsp. nov. 



GILA POCKET MOUSE. 



Type from Tinajas Altas, Gila Mountains, Yuma County, Arizona (alti- 

 tude 1,400 feet). No. 203003, 9 adult, U.S. National Museum (Biologi- 



