112 Bailey North American Species of Sigmodon. 



of type: basal length 28.4; nasals 12.5; zygomatic breadth 18; mastoid 

 breadth 13; alveolar length of upper molar series 5.5. 



Distribution. Northern Yucatan and Campeche. 



Specimens examined. Total number 45, from the following localities: 



Yucatan: Puerto Morelos 2, La Vega 5, Tunkas 5, Chichen Itza 20. 



Campeche: Apazote 17. 



Remarks. From toltecus this form is readily distinguished by darker 

 coloration and brown instead of gray feet, from saturatus by duller 

 colors and smaller size, and from both by its very light dentition. 

 Specimens from Apazote and Chichen Itza are grading toward saturatus. 



Sigmodon hispidus borucae Allen. 



Sigmodon borucae Allen, Bull. Am. Mus. Nat. Hist. IX, 40, March 11, 

 1897. 



Type locality. Boruca, Costa Rica. 



General characters. Size medium, about as in berlandieri, pelage 

 rather soft. 



Color. Upperparts dull yellowish brown; belly grayish or buffy white; 

 feet grayish brown; tail blackish above, grayish brown below. 



Skull. Nearest to that of saturatus but distinguished by the smaller, 

 flatter audital bullae, and other slight characters. 



Measurements. Type (from original description): total length 275; 

 tail 115; hind foot (measured dry) 30. Skull: basal length 29; nasals 12; 

 zygomatic breadth 18; length of upper tooth row 5.5. 



Distribution. Costa Rica; specimens examined from the type locality 

 only. 



Remarks. Sigmodon h. borucae belongs to the toltecus group of rather 

 small, dark colored forms, but shows good subspecific characters, differ 

 ing from toltecus in darker coloration, brown instead of gray feet, heavier 

 dentition and other slight skull characters; from microdon in larger size, 

 longer tail, heavier dentition and flatter audital bullae; from typical 

 saturatus in duller coloration, longer tail, flatter audital bullae; but 

 from Guatemala specimens of saturatus it does not differ in color. 



Sigmodon alleni sp. nov. 



Type from San Sebastian, Mascota, Jalisco, Mexico, No. 88,227, U. S. 

 National Museum, Biological Survey Collection, $ ad. Collected 

 March 15, 1897 by E. W. Nelson and E. A. Goldman. Original No. 

 10,708. 



General characters. Size of berlandieri but with slenderer feet and 

 tail, smaller molars, brighter colors, and softer pelage; pelage fine and 

 not hispid in winter or summer. 



Color. Upperparts dull tawny; belly white or buffy; feet yellowish 

 brown; tail black above and brownish below. Young, dark umber 

 brown, soon becoming tawny. 



