SIGMODONTOMYS. RHITHRODONTOMYS. 255 



zygoma broad with no anterior point; parietal large, exterior bor- 

 ders longest; first upper molar with two deep internal reentrant 

 angles, second molar with one, third none; first lower molar with 

 two deep external reentrant 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 vertebrae, 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 

 Muridce, 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. Kliithrodoiitomys. Harvest Mice. 



J. A. Allen, On the species of the genus Rheithrodontomys (sic) 

 Bull. Am. Mus. Nat. Hist., 1895, P- I0 7- 



*The skull of the unique specimen of this species having been lost, it was 

 not possible to illustrate the genus 



