1914.] 



EEITHEODOK"TOMYS MEGALOTIS GROUP. 



39 



REITHRODONTOMYS MEGALOTIS ZACATEC^ Merriam. 



Mountain Harvest Mouse. 



(PI. I, fig. 11; PI. IV, fig. 11.) 



Reithrodontomys megalotis zacatecx Merriam, Proc. Wash. Acad. Sci., Ill, 1901, p. 557. 

 Reithrodontomys megalotis obscurus Merriam, Proc. Wash. Acad. Sci., Ill, 1901, 



p. 558 (Sierra Madre, near Guadalupe y Calvo, Chihuahua). 

 Reithrodontomys colimse Allen, Bull. Am. Mus. Nat. Hist., XXII, 1906, p. 249 (not 



of Merriam; specimens from Volcan de Fuego, Jalisco). 



Type locality. — Valparaiso Mountains, Zacatecas, Mexico. 



Distribution. — Mountains of Western Mexico, from southern 

 Chihuahua to Michoacan. 



Characters. — Very similar to arizonensis, but with darker uncler- 

 parts; smaller and paler than saturatus, with less black on upperparts. 



Color. — Adults: Upperparts ochraceous-buff, heavily mixed with 

 black, the ochraceous color most pronounced on head and sides; 

 the black predominating on dorsal area but not forming a distinct 

 band; underparts washed with ochraceous-buff, this color usually 

 most intense between the fore legs; ears fuscous or dark hair-brown, 

 usually mth a blackish patch on lower inner margin; feet w^hitish 

 or buffy white, ankles dusky; tail sharply bicolor, dark hair-brown 

 above, grayish white beneath. Young: Paler and grayer on upper- 

 parts; sides with a well-marked lateral line of light ochraceous-buff; 

 underparts whiter. 



Sliull. — Similar to that of megalotis but smaller; rostrum slenderer, 

 narrowed at the tip; zygomata sHghtly narrower anteriorly; nasals 

 narrowed to a point posteriorly, ending on a Hne with premaxillse. 



Measurements. — Average of 3 adults from type locality: Total 

 length, 154; tail vertebrse, 84; hind foot, 18.5. Average of 3 adults 

 from Guadalupe y Calvo, Chihuahua: 160; 85; 18. Skull: (See 

 table, p. 81). 



RemarJcs. — This subspecies is a small, dark-colored race of megalotis 

 inhabiting the mountains of western Mexico. No specimens have 

 been seen indicating intergradation between megalotis and zacatecse, 

 but very hkely such material may in the future be secured. Inter- 

 gradation with saturatus is indicated by specimens from the State of 

 Mexico (Salazar, Toluca Valley, etc.) which resemble saturatus in color 

 but have smaller ears and skulls intermediate in size between the two 

 forms. From Nahuatzin, Michoacan, specimens nearly typical of both 

 forms are at hand. Some are larger with larger, darker ears and large 

 skulls (as in saturatus), but at least 2 adult individuals, by reason 

 of small size, small skull, small ears, and ochraceous underparts, 

 must be referred to zacatecx. Specimens from Patamban, Michoacan, 

 average more intensely ochraceous, especially on the underparts, 

 and have more black on the ears, but are otherwise typical. The 



