VOL. XII, PP. 115-125 APRIL 30, 1898 



PROCEEDINGS 



OF THE 



BIOLOGICAL SOCIETY OF WASHINGTON 



DESCRIPTIONS OF TWENTY NEW SPECIES AND 



A NEW SUBGENUS OF PEROMYSCUS FROM 



MEXICO AND GUATEMALA. 



BY C. HART MERRIAM. 



The enormous collection of mice of the genus Peromyscus made 

 in Mexico and Guatemala by Mr. E. W. Nelson and his assistant, 

 Mr. E. A. Goldman, contains many novelties, some of which are 

 here described. Two of the new species, the largest yet discov 

 ered, are separated subgenerically under the name Megadontomys. 

 Seven of the others belong to a well marked group distinguished 

 by rather large size, long, soft and very dense fur, dark color, and 

 a general agreement in cranial and dental characters.* It is but 

 a step from P. guatemalensis of this series to totontepecus of the 

 mexicanus series, and another step covers the related tehuantepecus 

 and oaxacensis. Three others (felipensis, gratus, and levipes) be 

 long to the truei-difficilis group, of which P. hylocetes may be an 

 aberrant member, and one (musculoides) is distantly connected 

 with the leucopus series. Standing widely apart from all of these 

 is P. mekisturus, an extraordinary long-tailed animal, perhaps 

 arboreal, from the mountain slope at Chalchicomula, Puebla. 



Subgenus MEGADONTOMYS nobis. 



Type, Peromyscus (Megadontomys) thomasi sp. nov., from Mts. near Chil- 

 pancingo, Guerrero, Mexico. 



Characters. Size large (the two known species as large as roof rats) ; ears 

 and tail long and very scantily haired ; pelage long, soft, and very dense. 



* The new species in the series in question are : zahrynchus, guatemalen 

 sis, lepturns, and the slightly divergent megaiops, aurilas, and comptus. 



27 Bior. Soc. WASH, VOL. XII, 1898 (115) 



