1914.] 



BEITHKODONTOMYS RUFESCENS GROUP. 



61 



Measurements. — Type ($ ad.): Total length, 190; tail vertebrae, 

 110; hind foot, 20; ear from notch, 14.5; topotype ( ad.): 182; 

 99; 21. Skull: (See table, p. 81). 



Remarks. — ^This form closely resembles R. rufescens luteolus, both 

 in color and in the character of the pelage, which is shorter and less 

 wooly than in R. colimse colimse, which lives at higher altitudes. 

 Compared with luteolus the present form is a slightly paler shade of 

 ochraceous-buff. Its skull characters indicate close relationship to 

 colimse and necessitate its separation from luteolus, but additional 

 material may serve to connect the two groups, making luteolus a sub- 

 species of colimse. 



Specimens examined. — Two, from type locality. 



REITHRODONTOMYS DORSALIS Merriam. 

 Black-backed Harvest Mouse. 

 (PL II, fig. 4; PI. V, fig. 4.) 

 Reithrodontomys dorsalis Merriam, Proc. Wash. Acad. Sci, III, 1901, p. 557. 



Type locality. — Calel, Guatemala. 



Distribution. — Highlands of Chiapas and Guatemala. 



CTiaracters. — Smaller than R. rufescens luteolus, with blacker back 

 and paler sides; skull with higher braincase. 



Color. — FresJb pelage (January): Upperparts ochraceous-buff, 

 mixed with black, with a well-defined median band or stripe of black; 

 sides varying from ochraceous-buff to pinkish cinnamon, sometimes 

 with a rather pronounced lateral line next to the belly; underparts 

 washed with light ochraceous-buff; ears fuscous-black, darker than 

 in luteolus; tail bicolor, fuscous above, grayish white beneath; hind 

 feet grayish white; front feet buffy with a dusky stripe reaching half- 

 way to the toes. Worn pelage: General tone redder (pinkish cinna- 

 mon to pale tawny) ; black dorsal area much less clearly defined. 



Skull. — Resembling that of R. r. rufescens in general shape, but 

 averaging smaller, with larger bullae. Compared with R. r. luteolus: 

 Smaller; braincase decidedly more inflated; interpterygoid fossa 

 much narrower. Compared with saturatus: Larger, with heavier 

 rostrum and more widely expanded zygomata. The upper molars 

 in a majority of the specimens examined have a simple enamel pat- 

 tern, but some specimens show an incomplete subsidiary loop and 

 well-developed accessory tubercles on the outer border, thus com- 

 pletely bridging the gap between the two subgenera. 



Measurements. — Average of 10 specimens (adult and subadult) from 

 type locality: Total length, 167.5 (160-175); tail vertebras, 90 (82-96); 

 huid foot, 19.3 (19-20). Skull: (See table, p. 81). 



Remarks. — This species, although clearly belonging to the rufescens 

 group, seems not to intergrade with luteolus, its nearest neighbor on 



