156 Proceedings of the Biological Society of Washington. 



forms of the genus, but braincase and posterior part of frontal region 

 broader than in any of them ; rostrum rather slender. 



Measurements. — Type: Total length, 256; tail vertebrae, 125; hind foot, 

 26.5. Skull (type): Greatest length, 31.7; zygomatic breadth, 28.4; 

 interorbital breadth, 6.6; greatest width between temporal ridges, 14.6; 

 length of nasals, 10.6; length of anterior palatine foramina, 5.2; length 

 of palatal bridge, 5.2; alveolar length of upper molar series, 4.6. 



Specimens examined. — Total number 3, as follows: 



Costa Rica: Pacuare, 1. 



Nicaragua: Escondido River (45 miles from Bluefields), 1; Grey town 

 (type locality), 1. 



Remarks.— The members of the genus Nyctomys are slightly differ- 

 entiated and clearly assignable to a single species recognizable sub- 

 specifically as follows: 



Nyctomys sumichrasti sumichrasti (Saussure), eastern slope of mountains 



in State of Vera Cruz, Mexico. 

 Nyctomys sumichrasti salvini Tomes, Duenas, Guatemala. 

 Nyctomys sumichrasti decolorus (True), Rio de las Piedras, Honduras. 

 Nyctomys sumichrasti nitellinus Bangs, Boquete, Panama. 

 Nyctomys sumichrasti venustulus Goldman, Greytown, Nicaragua. 



