112 Proceedings of the Biological Society of Washington. 



Remarks. — In small size and pale coloration, as well as cranial details, 

 this bushy tailed woodrat contrasts strongly with N. c. cinerea, which 

 includes the greater part of Nevada in its wide range. While adults are 

 similar to N. c. arizonse and N. c. rupicola in color, the young are much 

 grayer and the cranial characters pointed out are distinctive. The audital 

 bullae are normally developed, not relatively enlarged as in the geographic 

 neighbor, N. c. arizonse. Like that of N. c. arizonse the tail is reduced 

 in bushy amplitude in comparison with the more northern subspecies. 



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



Perodipus ordii luteolus, subsp. nov. 



WYOMING KANGAROO RAT. 



Type from Casper, Wyoming. No. 160,408, cT adult, U. S. National 

 Museum (Biological Survey collection), collected by Merritt Cary, Sep- 

 tember 2, 1909. Original number 1690. 



General characters. — A large, pallid, long-tailed subspecies with mode- 

 rately developed maxillary arches, and mastoid and audital bullae. Most 

 closely allied to Perodipus ordii richardsoni. but general external dimen- 

 sions greater; tail and hind foot longer; color paler; skull differing 

 especially in reduction of maxillary arches. Closely resembling Perodipus 

 ordii longipes in general size and color, but mastoid and audital bullae 

 much smaller. 



Color. — Fresh pelage (September) : Upperparts in general varying 

 shades between light buff and light ochraceous-buff (Ridgway, 1912), 

 purest on cheeks, shoulders and sides, inconspicuously lined with black 

 over top of head and back; underparts, supraorbital and postauricular 

 spots, forelimbs, upper surface of hind feet, sides of tail and the usual hip 

 stripes pure white; top of nose, base of longer vibrissas, narrow orbital 

 rings, inner surface of ears, plantar surface of hind feet, and upper and 

 under sides of tail more or less distinctly blackish. Worn pelage : Upper- 

 parts slightly darker, more ochraceous-buffy and dusky markings faded. 

 Young (in first pelage) : About like adults but dark markings, especially 

 crested tip of tail, more distinctly blackish. 



Skull. — General size and form much as in P. o. richardsoni, but max- 

 illary arches less developed between lachrymals and jugals, the posterior 

 angle less prominent; interparietal and superior surface of supraoccipital 

 less depressed ; braincase tending toward greater inflation and consequent 

 expansion of the frontal region ; mastoid and audital bullae about as in 

 richardsoni. Similar in size to that of P. o. longipes, but mastoid and 

 audital bullae decidedly smaller. 



Measurements. — Type: Greatest length, 272; tail vertebrae, 154; hind 

 foot, 42. Average of three adults, including type, from type locality: 263 

 (258-272); 150 (147-154); 41.5 (41-42). Skull (type): Greatest length 

 on median line, 38.1; greatest breadth (between outer sides of audital 

 ' bullae), 24.3; breadth across maxillary arches, 21.2; least width of supra- 

 occipital (near interparietal), 2.8; maxillary toothrow, 4.8. 



Remarks. — The range of this subspecies includes Wyoming, southeastern 



