542 MONOGRAPHS OF NORTH AMERICAN RODENTIA, 
This form of the genus appears to have been first noted by Dr. Wood- 
house in 1853. His specimens were from El] Paso. The known limits of its 
distribution were enlarged in 1857 to include the region of the Platte; while 
specimens still more recently examined show that it extends northward to the 
Yellowstone at least, further east in Dakota, Nebraska, and Kansas than was 
formerly supposed, and even reaches to Arkansas, where specimens were 
lately procured at Fort Cobb. 
Nore.—The special papers in which the Saccomyide have been treated 
will be found quoted passim in this article; these citations constituting that 
portion of the bibliography of the family which I have compiled. 
