272 PROCEEDINGS OF THE ACADEMY OP 



A CRITICAL REVIEW OF THE NORTH AMERICAN SACCOMYID.E. 

 BY DR. ELLIOTT COUES, U. S. A. 



The small group of Rodents to be here treated consists of the 

 genera Saccomys, Heteromys, Dipodomys, Cricetodipus, and 

 Perognathus. 1 The animals are confined to North and Middle 

 America and the West Indies. They are immediately recognized 

 by the presence of ample cheek pouches, opening exteriorly and 

 lined with fur, in connection with their general murine aspect 

 for the Geomidse (Geomys and Thomomys), the only other rodents 

 which have the same kind of cheek pouches, have an arvicoline 

 contour, and are altogether different in external appearance. 



This group appears to have been first put together at any 

 rate it was first satisfactorily defined in 1857, by Professor 

 Baird, Avho made it a subfamily {Saccomyinae) of Geomyid.se. 

 This sagacious naturalist seems to have been the first to perceive 

 and act upon the really very close affinities subsisting between 

 the Saccomyidse and Geomyidse, which had previously been widely 

 separated in the system ; but, in recognizing these relationships, 

 he was led to the length of uniting the two groups as one family. 

 As I have already shown, 2 the curiously different shape of the 

 Geomyidse and Saccomyidse, which is of course only a matter of 

 secondary consequence, is co-ordinated with structural characters 

 of prime importance, fully warranting the erection of the Sacco- 

 myinse into a family Saccomyidse, distinct from, though unques- 

 tionably standing next to, the Geomyidse. 



We may consider that this fact was effectually, though only inci- 

 dentally, exhibited in 1808, by Dr. J. E. Gray, in his "Synopsis of 

 the Species of Saccomyidai, or Pouched Mice, in the Collection of 

 the British Museum." (P. Z. S. 1868, pp. 199-206.) Though 

 using a terminology indicative of a subfamily (" Saccomyinae"), 

 this author speaks of " the family" of Pouched Mice. 



In his "Arrangement of the Families of Mammals," 1812, Dr. 

 Gill first formall}' catalogues a family Saccomyidse, equivalent 



1 Abromys, Gray, P. Z. S. 1868, 202, is not included, because the diag- 

 nosis is insufficient for its recognition. It is probably Perognathus. 



2 Bulletin U. S. Geol. and Geogr. Survey of the Territories (Hayden's), 

 second series, No. 1, 1875, pp. . 



