MUS. ONYCHOMYS. 165 



BROWN* RAT. 



Type locality. Alexandria, Egypt. 



Geogr. Distr. Cosmopolitan. 



Gcnl. Char. Smaller than M. norvegicus; tail considerably longer 

 than head and body; annuli about 240. 



Color. Above yellowish brown tinged with reddish; flanks 

 grayish; under parts and upper surface of feet yellowish white; tail 

 dusky. 



Measurements. Total length, 356; tail vertebrae, 198; hind foot, 

 35. Skull: occipito-nasal length, 43; Hensel, 34; zygomatic width, 

 19; interorbital constriction, 6.5; length of nasals, 15; palatal length, 

 20; length of upper tooth row, 6.5. 



The next genus contains the Mole Mice, little creatures with a 

 soft, velvety pelage and rather short tails. They have usually a pale 

 coloration, with white or whitish belly, hands, and feet. 



41. Oiiycliomys. Mole Mice. 



Onychomys Baird, N. Am. Mamm., 1857, p. 458. Type Hypudaus 



leucogastcr, Max. 

 Hypudaus. Max., Reise, N. Am. 1841, p. 99. (nee Auct.) 



"Form arvicoline; tail less than half the body in length; claws 

 very large, fossorial, the anterior longest; soles with only four tuber- 

 cles, the two posterior of the other groups wanting; posterior two- 

 thirds of soles densely furred. Skull without orbital crest; the upper 

 margin of orbit sharp." 



KEY TO THE SPECIES AND SUBSPECIES. 



A. Tail slightly over one-fourth the total length PAGE 

 of head and body. 



a. Upper parts tawny cinnamon and black. . .O. melanophrys 166 



b. Upper parts pale cinnamon and little black. O. m. pallescens 166 



c. Upper parts grayish vinaceous buff O. ramona 167 



B. Tail one-third or over the total length of head 

 and body. 



a. Upper parts yellowish brown O. iorridus 167 



b. Upper parts drab gray 0. t. arcnicola 168 



c. Upper parts cinereous O. t. perpallidus 168 



d. Upper parts ashy vinaceous O. macrotis 169 



