472 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 52 



MUS PEROMYSCUS, sp. nov. 

 (Plate LVI, b, skull, natural size) 



Type No. 161905, U. S. Nat. Mus., adult male (skin and skull) ; 

 Njoro O Nyiro, Sotik, British East Africa; June 9, 1909; collected 

 t)y E. Heller; original No. loii. 



General characters. — Skull long and narrow with slender ap- 

 pressed zygomatic arches and produced rostrum ; molar series short 

 and narrow with the internal cusps illy defined ; ears large, rounded, 

 scantily clothed by minute hairs ; tail essentially naked. 



Color. — Upperparts sepia changing gradually to walnut-brown 

 posteriorly ; sides mixed grayish and fulvous, the transition to the gray 

 of the underparts rather abrupt ;sidesof head and base of ears lighter 

 "brown, similar to the coloration of the rump ; underparts and feet 

 light grayish, with faint median fulvous wash ; tail dusky. 



Measurements. — Head and body, 135; tail, 146; hind foot, 26; 

 ear, 22. Skull: condylobasal length, 30.4; zygomatic breadth, 16.0; 

 interorbital constriction, 5.0 ; mastoid breadth, 12.8 ; depth of brain- 

 case at middle, 0.0; nasal, 12.8; diastema, 8.6; mandible, 19.0; max- 

 illary toothrow (crowns), 5.0; mandibular toothrow (alveoli), 5.0. 



