170 Merriam — DescTiptions of Nine New Mammals. 



the transverse loops long and narrow, tlie inner reentrant angles 

 abont twice as deep as the outer ; first lower molar with anterior 

 l()o[) double, forming a projecting antero-external loo}) and an 

 internal lateral loop. 



Mr. Nelson says of it : "A small wood rat was found living in 

 crevices in the rocks, at an elevation of 12,000 feet, on the north 

 slope of the Sierra Nevada de Colima." This is in the upper 

 fir belt. 



At Zapotlan, in tlie valley l)elow, he obtained five specimens 

 of a form similar to the present but slightly larger and with con- 

 color tails. 



Genus Sitomys. 



Among the small rodents collected are numerous specimens 

 of two mice wdiich in general ajipearance look almost i:)recisely 

 like the connnon house mouse {Mu^ miiseidus), but are still 

 smaller and have shorter tails. They may be roughly separated 

 into two series, according to size. The smaller is a form (or 

 subspecies) of Sitomys Unjloru which was described ]>v Mr. Old- 

 field Thomas a few years ago from specimens o])tained at San 

 Diego, Duval count3% Texas; the larger apparently is an unde- 

 scribed sj^ecies, here designated as 



Sitomys musculus ^p. nuv. 



Type No. \l\ll (^ ^<b ^- ^- Nutional ^Museum (De[)artiiK'nt of Agri- 

 culture collection). From near Cblima City, Mexico, March 9, 1892. 

 Collected by E. AV. Nelson. (Original number, 2055.) 



Measuremetits (in millimeters, taken in tlesh l)y collector). — 

 Total length, 123 ; tail vertebra^, 48 ; hairs, 1 ; hind foot, 17 ; ear 

 (in dry skin) from anterior root, 5.5. 



General Ch(iracter>i. — In size, color, and external appearance 

 Sitovrijs Diiisnihis looks almost exactly like a small common 

 house mouse (Mu>< in nsrii! >(>;), exce])t tliat the tail is shorter. It 

 is smaller than any known species of Sitouii/s excej)! -S'. fai/lon, 

 from which it differs in being somewhat larger, with longer ears 

 and tail and larger hind feet. It is not quite so dark as typical 

 *S'. taylori, either above or below. The hind feet measure 16 or 17 

 mm., while those of S. taylori measure only 13 or 13.5. Twenty- 



