NO. 2057. THE GRASSHOPPER MICE—HOLLISTER. 447 



ONYCHOMYS LEXTCOGASTER FTJXIGINOSTTS Merriam, 



1890. Onychomys fuliginosus Merriam, North Arner. Fauna, No. 3, p. 59. 

 September 11. 



Type-locality. — Black Tank lava beds, northeast of San Francisco 

 Mountain, Arizona. 



. OeograpJiic distribution. — Lava beds and pinyon and cedar belt 

 east and northeast of San Francisco Mountain, Arizona. 



General characters. — Coloration very dark; characters otherwise as 

 in melanophrys. 



Color. — Old adult in autumn (17997, Black Tank, Arizona, Septem- 

 ber 27; type) : Upperparts dark blackish brown; darkest on head and 

 along middle of back to tail, where the color is almost deep neutral 

 gray; sides lighter, more wood-brown; ear tufts not conspicuous, the 

 color of head; outer sides of legs to foot color of back; tail blackish- 

 brown above at base, paUng to near end, which is white like the lower 

 surface. Arms, hands, and feet whitish; underparts of body white. 

 The color of upperparts extends downward on sides much farther 

 than usual in the genus, leaving only the ventral surface pure white. 

 A younger adult from the type-locality (17996, September 21) lacks 

 most of the smoky coloration and is a rich dark wood-brown, mottled 

 with blackish-brown, above; the legs are nearer white, as usual in 

 the group, with only a faint indication of color along outer side to 

 near heel. Three immature specimens also exhibit this variation in 

 color and markings; two are like the type and one is hke the last- 

 described specimen. 



Skull. — The skull does not differ in any essential respect from that 

 of melanophrys. 



Measurements. — Type: Total length, 160 milUmeters; tail vertebrae, 

 47; hind foot, 21.5; ear from notch in dry skin, 15.0. Skull: Con- 

 dylobasal length, 25.9; zygomatic breadth, 15.8; interorbital breadth, 

 5.2; breadth of braincase, 13.2; length of nasals, 11.6; length of 

 mandible, 15.4; maxillary tooth row, 4.5. For detailed measure- 

 ments of specimens, see page 477. 



Type-specimen. — No. iHfJ, United States National Museum, 

 Biological Survey collection. vSkin and skull of old adult female 

 (teeth much worn). Collected September 27, 1889, by Dr. C. Hart 

 Merriam and Vernon Bailey. Original number, 547. 



Remarks. — This is a local lava-bed form of melanophrys. Such 

 local variations occur in other rodent genera, notably Peromyscus 

 and Neotoma, in the ^'malpais" sections of Arizona and New Mexico. 

 There is a question, perhaps, if such extreme local color variations 

 should be recognized by name, but until more material from the 

 vicinity of San Francisco Mountain is examined it seems best, in 

 this case, to retain the form as a subspecies. Specimens of melan- 

 ophrys from Walnut, Arizona, show a tendency toward fuliginosus 



