SIGMODONTOMYS. RHITHRODONTOMYS. 255 
zygoma broad with no anterior point; parietal large, exterior bor- 
ders longest; first upper molar with two deep internal reéntrant 
angles, second molar with one, third none; first lower molar with 
two deep external reéntrant angles, and one on both the second and 
third molars. 
248. *alfari (Sigmodontomys), Allen, Bull. Am. Mus. Nat. Hist., 1897, 
P. 39- 
ALFARO’S Rice Rat. : 
Type locality. Jimenez, Costa Rica. Altitude, 700 feet. 
Geogr. Distr. Costa Rica, Central America; range unknown. 
Genl. Char. Similar to Sigmodon; fur long, soft, thick; tail 
longer than head and body; hind feet large, naked; tail naked; ears 
small. 
Color. Upper parts yellowish brown, with dorsal region dusky 
brown; beneath grayish white; tail naked, dark brown; fore feet 
pale brown passing to grayish on toes; hind feet naked, grayish 
brown; ears blackish brown. 
Measurements. Total length, 278; tail vertebre, 155; hind foot, 
37; ear, 14. Skull: total length, 35.2; basal length, 25.4; interor- 
bital constriction, 12; width of braincase, 13.2; length of nasals, 
14.3; palatal length, 15; length of upper tooth row, 5.3; length of 
mandible, 18. (ex Type.) 
The genus RHITHRODONTOMYs contains the smallest species of the 
Muride, some indeed much smaller than certain species of shrews, 
in which family are found the least in size of American mammals. 
The Harvest Mice in general are about half the size of the house 
mouse and not unlike that animal in color, but usually have brighter 
flanks and a whiter under body. Although the Harvest Mice have 
been separated into various species and races, they are very difficult 
to distinguish, for there is a very great general resemblance among 
them all. 
52. Rhithrodontomys. Harvest Mice. 
r— ee oe 
J. A. Allen, On the species of the genus Rheithrodontomys (sic) 
Bull. Am. Mus. Nat. Hist., 1895, p. 107. 
*The skull of the unique specimen of this species having been lost, it was 
not possible to illustrate the genus 
