44 University of California Puhlications in Zoology [Vol. 21 



From P. tularensis Merriam, P. elephantinus differs in much larger 

 size, much larger ear, darker general coloration, heavier dentition, 

 much larger mastoid and auditors^ bullae, less strongly angled max- 

 illary arch, heavier malar bar, and in much heavier rostrum, the end 

 of which flares conspicuously. From P. agilis, P. elephaiitimis differs 

 greatly in general size (though not in coloration), the ear is very much 

 larger, the rostrum heavier, the nasals flare at their ends, and the 

 bullae are proportionally greater in size. Other details of difference 

 are numerous, but each seems to be correlated more or less directly 

 with one or more of the several features already noted. 



Measurements. — The average measurements of ten adult speci- 

 mens, five males and five females, are as follows : total length 324 mm. ; 

 tail vertebrae 197 mm. ; hind foot 46.8 mm. ; ear from crown 17.4 mm. ; 

 greatest length of skull 43.0 mm. ; width of skull across bullae 

 26.3 mm. ; greatest length of nasals 15.7 mm. ; width of rostrum near 

 end 4.8 mm. ; width of maxillary arch at middle 5.2 mm. 



Distribution. — The only material at hand representative of this 

 species is from the tj'pe locality, as specified above. This consists of 

 twenty-seven skins with skulls, adults and young, taken July 8 to 

 July 21, 1918, by the Museum field men, Halsted G. White and 

 Eichard M. Hunt. So far as ascertained up to the present time this 

 mammal is an exclusive inhabitant of dense chaparral. 



Remarks. — The relationship of this form with any one of the other 

 Californian species which have been previously described is not close ; 

 P. elephantiuKS, in combination of characters, stands quite alone. 

 The very large ear and its shape and manner of folding has suggested 

 the name selected. 



Perodipus swarthi, new species 

 Carrizo Plain Kangaroo Rat 



Type. — Male adult, skin and skull; no. 14440, Mus. Vert. Zool. ; 

 seven miles southeast of Simmler, Carrizo Plain, San Luis Obispo 

 County, California; May 26, 1911; collected by H. S. Swarth and 

 W. L. Chandler; original no. 9144, H.S.S. 



Diagnosis. — Most nearly resembles Perodipus tularensis Merriam, 

 from which it differs in brighter ochraceous-buff coloration, larger 

 skull, and decidedly more inflated bullae. 



Comparisons. — ^This is the most brightly colored, that is, the most 

 clearly ochraceous-buff, of all the species of Perodipus so far known 

 from west of the desert divides. The bullar inflation is near the 

 maximum, relatively to general size of skull. 



Measurements. — The average measurements of six adult specimens, 

 two males and four females, are as follows : total length 297 mm. ; 

 tail vertebrae 175 mm. ; hind foot 43.5 mm. ; ear, from crown, 11 mm. ; 

 greatest length of skull 41.1 mm. ; breadth of skull across bullae 

 25.8 mm. ; greatest length of nasals 15.0 mm. ; width of rostrum near 

 end 4.1 mm. ; width of maxillary arch at middle 5.1 mm. 



