1908.] Allen, Mammals from Nicaragua. 657 



Represented by three specimens, all from the type locality and all collected 

 August 18, 1904, by Mr. M. A. Carriker, Jr. 



cam'kcri belongs to the same group as 0. alfaroi of Costa 

 Rica, O. gracUis of Ecuador, 0. rclutinus of northeastern Colombia, and 

 O. viUosus of Trinidad. It differs from 0. alfaroi in its much darker 

 coloration above, suffused with ochraceous instead of pale yellow, and in 

 being nearly twice larger. In size and coloration it approaches O. villosus 

 and O. velnihinx, especially the latter, some of the adult topotypes of which 

 are almost indistinguishable in coloration from 0. carrikeri, but the ears in 

 both the Trinidad and Colombian species are fully twice the size of those 

 of carrikcri, while the cranial differences are strongly marked. 



0. talam-ancce, also from Talamanca, belongs to a quite different group, 1 

 in a general way resembling 0. costaricensis, but about twice the size of 

 that species.] 



32. Sigmodon hispidus griseus subsp. nov. 



Type, No. 28497, c? ad., Chontales (in the coast lowlands), Nicaragua, Feb. 20, 

 1908; W. B. Richardson. 



General color above dark gray; underparts whitish gray. Middle of dorsal 

 region, from front of eyes to base of tail, gray, heavily lined with black; sides lighter, 

 more yellowish gray and less varied with black; feet gray; tail blackish brown 

 above, somewhat lighter below, very slightly haired. 



Three adults (collector's measurements), total length, 280-300 mm.; tail, 

 110-130; hind foot (skin), 31. 



This form differs from 8. h. borucce, its nearest known geographical ally, 

 in the gray color of the dorsal surface, which agrees almost exactly with that 

 of average specimens of 8. h. littoralis from Florida, to which in coloration 

 it bears a striking resemblance. It further differs from borucas in the form 

 of the skull, which is much broader in proportion to the length. Thus, in 

 comparable skulls, the total length in griseus is 37 mm., with a zygomatic 

 breadth of 21.5; in borucas these measurements are respectively 38 and 20.5. 

 The pelage of griseus is harsher and coarser than in borucce. 



Of the 9 adult specimens in the present series 7 are gray like the type 

 above described, while one has a slight suffusion of rufous, but much less 

 than average specimens of borucce. The other adult specimen is in abnormal 

 pelage, which in both color and texture greatly resembles that of a half- 

 grown brown house rat (Mus norvegicus). The two young examples 

 (nurslings) are much darker than borucas of corresponding age, and the 

 suffusion is pale fulvous instead of rufous. 



1 I am indebted to Dr. M. W. Lyon, Jr., Assistant Curator, Division of Mammals, U. S. 

 National Museum, for an opportunity to reexamine the type of O. talamancce in the present 

 connection. 



[October, 1908.] 42 



