106 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 69 



Genus SIGMODON Say and Ord. Cotton Rats 



The members of this genus attain the size of common rats, but 

 are more robust in form with tails usually shorter than the body, 

 rather thick at the base and tapering rapidly to slender tips. The 

 ears are short, but broad and clothed with short fur. The pelage is 

 coarse, and grizzled grayish brown in general color. The skulls are 

 easily distinguished by a spinous process projecting forward from 

 the upper edge of the outer wall of the antorbital foramen. 



SIGMODON HISPIDUS CHIRIQUENSIS Allen 



Boqueron Cotton Rat 



Sigmodon borucce chiriquensis Allen, Bull. Amer. Mus. Nat. Hist., Vol. 20, 

 p. 68, February 29, 1904. Type from Boqueron, Chiriqui, Panama. 



The Boqueron cotton rat is very similar to vS\ h. borucce of Costa 

 Rica, but the upperparts are somewhat richer, more rufescent in 

 general tone. The underparts are usually white, but in both forms 

 they are sometimes suffused with buff. 



The basis of the subspecies is six specimens collected at Boqueron 

 by J. H. Batty. Alston (1879, P- I 5 2 ) notes examples of Sigmodon 

 hispidus " supplied to the British Museum by Whitely from 

 Veragua." As Sigmodon borucce, Bangs (1902, p. 32) lists measured 

 specimens taken by W. W. Brown, Jr., at Bugaba, which he says 

 " appear to be identical with Allen's S. borucce of Boruca, Costa 

 Rica." Thomas (1903a, p. 41) records eight examples "mostly 

 young," but probably referable to this form, from Cebaco Island off 

 the southwestern coast of Panama. Anthony (1916, p. 368) records 

 a specimen taken in a low grassy meadow near the Chagres River at 

 Gatun. 



Specimens from the Canal Zone are provisionally referred to this 

 form, although the grayer examples are practically indistinguishable 

 from typical S. h. borucce. 



Cotton rats are common only locally in the Canal Zone. At Gatun 

 a few were captured in the thick grass growing in places where the 

 forest has been cleared away. Such places are usually overgrown 

 with grass and a few small bushes, with here and there clumps of 

 larger bushes. The cotton rats make fairly well-trodden paths lead- 

 ing away, in various directions, from their holes which commonly 

 enter the ground along low banks. At Tabernilla they are abundant 

 in thick grass and small bushes which have overgrown earth and rock 

 excavated from Culebra cut and dumped there several years ago. 



