Vol. XXI, pp 197-198 October 20, 1908 



PROCEEDINGS 



OF THE 



BIOLOGICAL SOCIETY OF WASHINGTON 



A NEW HARVEST MOUSE FROM THE SALT MARSHES 

 OF SAX FRANCISCO BAY, CALIFORNIA. 



BY JOSEPH DIXON 

 Stanford University, California. 



For the past forty years Mr. Chase Littlejohn, of Redwood 

 City, lias been aware of the existence of a little red-bellied 

 mouse in the salt marshes of San Francisco Bay near his home; 

 but since the mouse was so common and well known to him he 

 supposed that it was one of the well known species. Last fall 

 he showed me a number of alcoholic specimens of this mouse 

 and wished to find out what it was. 



The material at hand was unsatisfactory to work with, so we 

 set to work to gather some new material which now consists of 

 some twenty-six study skins and skulls from various repre- 

 sentative points around San Francisco Bay. A close study of 

 this material led us to believe that the mouse was an unknown 

 form restricted to the salt marshes of San Francisco Bay. The 

 material was sent to Washington, and a comparison of it with 

 the material in the Biological Survey Collection resulted in the 

 decision that it was a " very good new form," which I hereby 

 describe as: 



Reithrodontomys raviventris sp. nov. 



Type. — male; number l7.">, collection of University of California Museum 

 of Vertebrate Zoology (original number, R'>4); Redwood City, San Mateo 

 County, Calif.; collected by Chase Littlejohn ; Jan. 15, L908. 



Geographic distribution. — Salt marshes of San Francisco Bay. 



Habitat. — Restricted to the salt marsh. During the winter and high 

 tides, they congregate along the old dikes and other high places, hut 

 during the summer they scatter out in the Salicornia toward the bay 

 shore. In the salt marsh near Palo Alto, this mouse was found using the 

 runways of Micro! us extensively. 



31— Proc. Biol, sec. Wash., Vol. XXI, 1908. (197) 



