66 NELSON 



ily overlaid with white. A male taken at same place (Jan. 19) is 

 similar but the white on upper surface is duller and the underparts rich 

 buff. 



Another male taken at Acapulco (Jan. 10) has the nape patch even 

 richer or darker rufous than usual ; top of nose and fore part of crown 

 clear iron gray; rest of upperparts dingy rusty red, grizzled with 

 grayish white ; feet and outside of thighs whiter ; underpai-ts bright 

 ferruginous, palest on throat and breast ; tail as usual heavily washed 

 with white. 



Two males from Acapulco (Jan. 11) are in a curious melanistic 

 condition : One has the nose and fore part of crown black, sparsely 

 grizzled with white, the nape and rump patches very rich dark rufous 

 washed with black, and the intermediate area along the back black, 

 finely grizzled with dark rusty; sides of head, neck and body black, 

 overlaid with fine grizzling of dark fulvous and dingy rufous; feet 

 glossy black ; tail black, thinly washed with white above and below, 

 with dark rusty rings near bases of hairs ; underparts smoky black 

 washed with fulvous brown and dull rusty. The other melanistic 

 specimen has the top of head as in the last ; the nape and rump patches 

 black, the rest of upper parts dull rusty brown grizzled with black 

 and more sparsely with white ; chin dark gray; throat grizzled rufous; 

 rest of underparts dark reddish brown becoming darker posteriorly ; 

 tail above black heavily overlaid with white; below black, heavily 

 bordered with white. 



A female taken at Llano Grande, Oaxaca (Feb. iS) has the nose 

 and fore part of crown black, grizzled with gray ; nape and rump 

 patches dingy rusty, heavily washed with black ; rest of back grizzled 

 reddish brown and black, shading into dark yellowish brown on sides ; 

 feet grizzled black and grayish brown; toes black; underparts dark 

 dingy buff ; tail above black, washed with white ; below, median band 

 buffy yellow with broad border of black, edged with white. 



Measurements. — Average of 5 adults from type locality : total 

 length 518.2 ; tail vertebrae 268 ; hind foot 66. 



Cranial characters. — Premolars \. Skull very similar to that of 

 S. socialis but somewhat shorter ; broader interorbitally ; upper molar 

 series slightly shorter. Five adult skulls from the type locality aver, 

 age: basal length 50.8; palatal length 26.5; interorbital breadth 19.3; 

 zygomatic breadth 33.7; length of upper molar series 10.6. 



General notes. — In the Zoology of the Voyage of the Venus, 

 under the name S. aureogaster., is a good figure of a white bellied 

 specimen of this species, which probably came from Acapulco. On 



