1919] 



Grinnell: New Kangaroo Bats -15 



Distrihidion.^he material at hand representing this ^Pecies con 

 sists of seven specimens, all from ponits near .^^g^^^l.^^^^!;^^^ .^^^^^^^^ 

 miles southeast of Simmler, on the Carrizo Plani, 2000 feet altitude, 

 San Luis Obispo County, California. 



Remarks.— The name is selected as a recognition of the success in 

 general vertebrate field work of Mr. Harry S. Swarth, of the statf ot 

 the Museum of Vertebrate Zoology. 



Perodipus dixoni, new species 

 Merced Kangaroo Rat 

 Type.-M^\e adult, skin and skull; no. 26805 Mus. Vert. ZooL; 

 Delhi near Merced River, in Merced County, California; March id, 

 1917 ;' collected by J. Dixon; original no. 5580. . 



Diaqnosis.-l medium-sized kangaroo rat, slightly darker m color 

 than Perodipus Udarensis Merriam, but paler than P streaton Mer- 

 riam. Bullae smaller, and rostrum and dentition much weaker than 



in either of those species. . 4. f ^^ 



Comparisons.-Perodipus dixoni is conspicuously diffeTenttom 

 P tularensis, its neighbor to the south on the floor of the San Joaquin 

 Val lev fcomparison of the skulls. The bullae are much less inflated, 

 «ie Isals are much shorter and iKtrrower, and the dentition is weake^. 

 The supraoccipital and interparietal, however, are quite as narrow 

 and tl e^-elative width and angulation of the maxillarj^ ^ -Z'^Tlt 

 Ihe same. As compared with P. streaton, the form belonging to the 

 Upper Sonoran zone of the adjacent Sierran slopes, the skul of 

 PdS..u is much smaller, and again the rostrum and bullae show 

 Ltd inferiority in volume, though, with the ^^^ -' ^t- ^^^ ^f,^^ 

 a decree as in the case of P. tularensis. Externally F dixom shows 

 LspecTal peculiarities except in dimensions; the body is smaller than 

 in either of its near neighbors, and its tail ^^^^latively longer^ 



Measurements.-The average measurements of ten adu^t ^i sub^ 

 adult specimens are as follows: total length 283 mm^; tail vertebrae 

 170 mm.; hind foot 41.1 mm.; ear, from crown, ^^-l mm. gieatest 

 leno-th of skull 37.0 mm.; breadth of skull across bullae 23.2 mm. , 

 greatest length of nasals 13.2 mm. ; width of rostrum near end 3.6 mm. ; 

 width of maxillary- arch at middle 4.8 mm. 



i).s'n^.^/.o>..-Material is at hand only from the east side of the 

 lower San Joaquin Valley, in Stanislaus and Merced counties, and is 

 rep?Leit d bySocalities as follows. Stanislaus County: three miles 

 south of La-range, 3. Merced County : near Delhi, 2 ; five miles north 

 of Snelling I2; mle and one-half miles south of Merced Falls, 1. 



Beniarlis—T\n^ new form is named in recognition of the pains- 

 taking quality of the field work carried on by Mr. Joseph Dixon m 

 the interests of the Museum of Vertebrate Zoology. It is through his 

 success in specially searching for kangaroo rats that some of our most 

 valuable specimens have been obtained. 



