Article III. DESCRIPTION OF A NEW SPECIES OF 

 SIGMODON FROM ECUADOR. 



By J. A. ALLEN. 



The material on which the present species is based was 

 kindly sent to me for determination by Mr. Oldfield Thomas, 

 Curator of Mammals at the British Museum, with permission 

 to describe it if new, and to retain the duplicates for this 

 Museum. While the species represented by this material is 

 nearly related to Sigmodon simonsi, it is well distinguished by 

 certain cranial differences and by the less intense fulvous 

 suffusion of the general pelage, especially that of the ventral 

 surface. 



Sigmondon puna, sp. nov. 



Type, No. 30, female ad., Coll. Perry O. Simons (British Museum), 

 Puna, Puna" Island, Ecuador, Nov. 10, 1898; altitude 10 m. 



Similar to Sigmodon simonsi Allen (this Bull., XIV, 1901, p. 40), 

 from Eten, Peru, but less suffused with buff, especially on the ventral 

 surface, which is only slightly or not at all tinged with pale buff in- 

 stead of being heavily washed with clear deep buff; fore and hind feet 

 grayer, and eye-ring paler. Skull with the anteorbital foramen much 

 broader, and hence larger and differently shaped; the bullae con- 

 siderably more swollen, the dentition weaker, and the rostral portion 

 of the skull shorter. 



Measurements. Head and body, 145; tail, 98; hind foot, 29; ear, 

 21 mm. Nine adults average: Head and body, 145 (140-160); tail, 98 

 (92-100, with one specimen 160); hind foot, 29 (28-30); ear, 20.6 

 (19-22). 



Skull. Type: Total length, 34; basal length, 30; palatal length, 

 16; length of nasals, 12; zygomatic breadth, 20; mastoid breadth, 

 14; interorbital constriction, 5; upper toothrow, 7. Six adult skulls 

 range in total length from 33-36, and in zygomatic breadth from 

 18.5-20. 



Sigmodon puna is represented by a series of 15 specimens 

 taken at Puna", Puna Island, during the first half of Novem- 

 ber, 1898, they being among the first specimens collected by 

 the late Perry O. Simons on the west coast of South America. 



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