MUS. ONYCHOMYS. 165 
Brown Rat. 
Type locality. Alexandria, Egypt. 
Geogr. Distr. Cosmopolitan. 
Genl. 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 vertebre, 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. Onychomys. Mole Mice. 
Onychomys Baird, N. Am. Mamm., 1857, p. 458. Type Hypudeus 
leucogaster, Max. 
Hypudeus. Max., Reise, N. Am. 1841, p. 99. (nec 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 voper parts. yellowish brown. .....22 2.2.2.3 O. torridus 167 
Peete Parts ATA STAY 550i. en ce O. t. arenitcola 168 
EeeLipper parts CinereQus:.... 2. 5.245 .k 2. O. t. perpalliidus 168 
ea pper: parts ashy “Vinaceous.. 50. 2 ae O. macrotis 169 
