2 o8 Bulletin A merican Museum of Natural History . [ Vol . X X 1 1 , 



occurred in a fossil state, they might prove extremely misleading and 

 be easily mistaken for characters of specific importance, or even of 

 generic value in the case of the premaxilla-maxilla-nasal modifica- 

 tions. I have on various occasions called attention to the wide range 

 of individual variation shown in cranial and other characters in a 

 large number of species of mammals, but generally without giving 

 graphic illustrations of them, and therefore take the present occasion to 

 illustrate by photography a few of the individually divergent speci- 

 mens in the present series of Escuinapa deer. 



6 Sciurus sinaloensis Nelson. 



Nineteen specimens: Escuinapa and vicinity, 10 specimens, Jan. 

 n, Feb. 18-27, March i, 18; Los Pieles, 6 specimens, April 4-19; 

 Juan Lisiarraga Mountain, (alt. 5500 ft.), 3 specimens, April 29-30, 

 May 5. 



" Found in the lowlands and foothills west of the Sierra Madre. Not 

 very common." J. H. B. 



Escuinapa, 8 males: Total length, 514 (502-537); head and 

 body, 249 (235-254); tail vertebrae, 265 (254-283) ; hind foot without 

 claws, 59 (57-60); ear from notch, 31 (2932). 



Los Pieles (alt. 3500 feet) and Juan Lisiarraga Mountain (alt. 

 5500 feet), 8 specimens, nearly all males: total length, 513 (502-540); 

 head and body, 249 (235-254); tail vertebras, 264 (254-286); hind 

 foot > 59 (54-63); ear, 29 (25-32). 



The range of this species is thus shown to extend from the low 

 arid coast region of southern Sinaloa eastward into the eastern foot- 

 hills of the Sierra Madre, to altitudes of 3500 and 5500 feet. The 

 specimens from the Sierra Madre foothills do not differ appreciably 

 in size (see above measurements) or color from those of the coast 

 region. 



7. Mus alexandrinus Geoffroy. 



Six specimens, Escuinapa, Dec. 27, Jan. i, 8, and Feb. 3, 5, 18. 

 "Found common in mangroves." J. H. B. 



8. Mus musculus Linn. 

 Six specimens, Escuinapa, Jan. 23, Feb. 3 and 19. 



9. Peromyscus spicilegus spicilegus (Allen). 



Twenty-three specimens, Escuinapa, Jan. 13, April 24-May 5. 

 Five of the 6 January specimens and one April specimen are in the 



