1914.] 



EEITHEODONTOMYS MEGALOTIS GROUP. 



41 



Characters. — Similar to longicaudus but larger and slightly paler. 



Color. — Worn spring pelage:^ Upperparts mixed light ochraceous- 

 buff and blackish brown, darkest on back, but without a distinct 

 dorsal stripe; underp arts white, tinged mth buff in pectoral region; 

 tail dark hair-brown above, white beneath; ears hair-brown, clothed 

 with ochraceous hairs. 



SlcuU. — Larger than that of R. m. longicaudus, but not otherwise 

 different. 



Measurements. — ^Average of 10 adults from type locality: Total 

 length, 169 (165-175); tail vertebrse, 94 (90-99); hind foot, 18.6 

 (18-19.5). Skull: (See table, p. 81). 



Remarlcs. — ^So far as known this is the only insular species in the 

 genus. Mr. C. P. Streator, who collected a series in 1892, found the 

 mice abundant on the island in brush and cactus. 



Specimens examined. — ^Twenty-eight, from type locality. 



REITHRODONTOMYS RAVIVENTRIS RAVIVENTRIS Dixon. 

 Red-bellied Harvest Mouse. 

 (PI. I, fig. 9; PI. IV, fig. 9.) 

 Reithrodontomys raviventris Dixon, Proc. Biol. Soc. Wash., XXI, 1908, p. 197. 



Type locality. — Redwood City, Cal. 



Distribution. — Salt marshes of San Francisco Bay, Cal. 



Characters. — Similar to R. megalotis longicaudus but upperparts 

 darker and imderp arts reddish; skull larger; tail shghtly shorter. 



Color. — Upperparts mixed black and pinkish cinnamon, the black 

 predominating on dorsal area; sides pale tawny in some individuals; 

 underparts pinkish cinnamon (rarely with a small white spot on chin) ; 

 ears black or fuscous on both surfaces, with a tuft of ochraceous hairs 

 at anterior base; hind feet and tail usually very dark, varying from 

 fuscous to clove-brown or sepia, the tail shghtly paler beneath, but 

 feet usually darker beneath; toes whitish; front feet sepia, often 

 tinged with buffy white. 



SlcuU. — Decidedly larger than that of R. m. longicaudus; with rela- 

 tively shorter rostrum; nasals and palatal foramina shorter; zygo- 

 mata more widely expanded anteriorly. 



Measurements. — ^Average of 21 from type locality: Total length, 

 130.7 (120-142); tail vertebrae, 64.8 (56-74); hind foot, 16.6 (15-18). 

 Average of 8 from Melrose Marsh, Alameda County: 137; 66; 17.7. 

 Skull: (See table, p. 81). 



Remarlcs. — This species is remarkable on account of its peculiar 

 characters and hmited distribution. It is the darkest form found 

 in the United States and the only one having reddish underparts. 

 In color it most nearly resembles R. australis of Costa Rica, but the 

 underparts are even darker than in that species. 



1 Fresh pelage not seen. 



