MAMMALS OF THE MEXICAN BOUNDARY. 457 



from topotypes of Baird's BeifhrothnfoiNys longicauda, his li. palUdus 

 tlius l)eeomintr a completo svnonyni of /?. longicauda, it is equally plain 

 that Allen's j^allidus is thorouo;hly composite, his table of 157 speci- 

 mens embracino; series of true longicauda and typical deseiii, which I 

 myself examined and measured in the field, from several localities on 

 the Colorado Desert and the Pacific slope, west of the Coast Range, 

 as well as specimens from the San Bernardino Valley and other locali- 

 ties, wdiich perhaps represented intergrades between the form of the 

 interior desert region {R. m. deserti) and that of the Pacific Coast strip 

 {R. longicauda). I regard it as probable that the four forms of the 

 R. megalotis group, named above, will eventually be proved to be 

 conspecific, in which case the latter three (arisonensis, deserti, and 

 longicauda) will have to stand as subspecies of Reitlirodoniornys mega- 

 lotis (Baird), which was the first one named. 



The several forms of this genus known from the region of the Bound- 

 ary may, perhaps, be identified by reference to the following 



KEY TO REITHRODONTOMYS FOUND ON THE MEXICAN BOUNDARY. 



a. Total length more than 1.50 mm. 



h. Total length less than 170 mm. Above yellowish Virown mixed with l)lack, but with- 

 out a darker vertebral area; sides faintly iuWovm. .Reifhrodonfomys laceyi (p. 458). 

 bh. Total length more than 170 mm. 



c. Length, 17S mm.; tail vertebr«>, 99; ear, 12. Above grayish brown with a yellow- 

 ish wash; sides strong yellowish fulvous; below dull whitish. 



Reithrodontomys mexicanus intermedius (p. 457). 

 cc. Length, 172 mm; tail vertebrsp, 99; ear, 14. Above pale yellowish brown, lined 

 with black, with a blackish median area; sides light yellowish; below white. 



Reithrodontomys fulvescens (p. 459). 

 aa. Total length less than 150 mm. 



d. Coloration pale, above yellowisli gray, lined with darker, and more fulvous on 

 sides. 

 e. Tail one-half the total length; color above yellowish gray, considerably mixed 



with blackish; pelage full and .soft .Reithrodontomys megalotis (p. 460). 



ee. Tail more than half the total length; color above yellowish, but little mixed 

 with darker; pelage short and .somewhat harsh. 



Reithrodontomys megalotis deserti (p. 462). 

 dd. Coloration dark; above yellowish brown, lined with blackish, with a darker 

 median dorsal area. 

 /. Length, 148 mm.; tail vertebra>, 77; hind foot, 17. Top of head grayish 



brown Reithrodontomys longicauda (p. 464). 



ff. Length, 149; tail vertebrje, 78; hind foot, 17. Top of head reddish brown. 



Reithrodontomys arizonensis (p. 459). 



REITHRODONTOMYS MEXICANUS INTERMEDIUS Allen. 



TAMATTLIPAS HARVEST -MOUSE. 



Reithrodontomys mexicanus intermedius Allen, Bull. Am. Mus. Nat. Hist., VII, p. 136, 

 May 21, 1895 (original description); VIII, 1896, p. 236 (in text).— Miller and 

 Rehn, Proc. Bo.st. Soc. Nat. Hist., XXX, No. 1, Dec. 27, 1901, p. 99 (Syst. 

 Results Study N. Am. Mam. to clo.se of 1900). 



