Merriam Little Known Kangaroo Rats. 141 



agrees with the topotypes of montanus. Externally it has the small ears 

 and relatively small, pale, crested tail of P. montanus, thus differing widely 

 from Dipodomys elator, which has larger ears and a long round tail ending 

 in a pure white brush about an inch in length, below which the upper and 

 under tail stripes are nearly black. The whitish tip in the type of montanus 

 is widely different, and results from the wearing off or suppression of the 

 pale brownish wash which usually suffuses the tips of the hairs. Some of 

 the topotypes are in exactly the same condition and match the type 

 perfectly. 



In comparing skulls of topotypes of P. montanus with those of D. elator, 

 it appears that montanus has weaker and narrower maxillary arches, 

 narrower nasals, narrower premaxillse, and narrower rostrum as a whole, 

 and also differs in the enamel face of the upper incisor teeth. In all of 

 these characters, the skull of Baird's type specimen, although not fully 

 adult and somewhat imperfect, agrees with the topotypes and departs from 

 D. elator. Furthermore, P. montanus came from the neighborhood of Fort 

 Garland at an altitude of nearly 8000 feet, in the upper part of the Transi 

 tion zone, while D. elator came from Henrietta, Texas, at an altitude of less 

 than 1000 feet and in the Lower Sonoran zone. 



Perodipus montanus may be known from the following description : 



Characters. Size medium or rather small ; tail rather short; ears small ; 

 upperparts dull buffy ochraceous, abundantly lined on the head with fine 

 dark-tipped hairs ; the back in summer pelage shading toward clay-color, 

 produced by brownish tips to the hairs ; end of nose above the small white 

 tip indistinctly dusky ; patch at base of whiskers dusky ; upper or interior 

 fold of ear pale fulvous, with a dark spot near the tip, followed by a small 

 whitish point which comes over from the back side of the ear, which is 

 mainly white ; upper tail stripe pale brownish drab, normally continuous 

 to extreme tip ; under tail stripe narrowing toward tip, and often absent 

 beyond end of vertebrae. 



Skull. Intermediate in size between ordi and richardsoni; rostrum, 

 nasals, and premaxillee rather narrow ; bullae rather large for size of skull ; 

 maxillary arch rather weak and narrow, but with well-developed rounded 

 outer angle ; supraoccipital and interparietal broad. The skull as a whole 

 closely resembles that of ordi, but is larger, the total length averaging about 

 38 mm. instead of 36. The maxillary arch is actually only a trifle larger 

 than in ordi, thus being relatively smaller. 



Measurements. Average of 40 specimens from type locality: Total 

 length, 250; tail vertebrae, 140; hind foot, 40.8. 



Perodipus ingens sp. nov. 



Type from Painted Rock, 20 miles southeast of Simmler, Carrizo Plain, 

 San Luis Obispo Co., California. Adult male, No. 128,805, U. S. National 

 Museum, Biological Survey Collection. August 6, 1903. Luther J. Gold 

 man. Original No. 777. 



