40 Bulletin American Museum of Natural History. [Vol. XX, 



1 8. Alouatta palliata mexicana Merriam. Nineteen speci- 

 mens, 1 6 adult and 3 nursing young, March 15 and April 8-19. 



Four adult males and 6 adult females have external meas- 

 urements as follows: 



$ , Total length, 1142: tail vertebrae, 585; hind foot, 145. 



$ , 1140; 620; 153. 



S, " 1212; " 635; " " 152. 



$ , 1115; 604; 153. 



? , 1189; " 661; " " 150. 



?, 1123; 630; 148. 



? , 1119; 605; " " 148. 



? , mo; " 620; " " 146. 



? , " 1107; " 618; " " 152. 



? , noo; 625; 148. 



Eight adult skulls, 3 males and 5 females, measure: Basal length, 

 (inner base of incisors to posterior border of occipital condyles), 3 

 males, 92.5 (9096); zygomatic breadth, 80.5 (78.583).: 5 females, 

 basal length, 83.4 (81-87); zygomatic breadth, 70 (68-72). 



Dr. Merriam, in separating this form (Proc. Biol. Soc. 

 Wash., XV, p. 67, March 22, 1902), indicated the distinctive 

 cranial features, but said nothing of the external differences, 

 which prove to be equally striking. Compared with a series 

 of seven specimens from Chiriqui, collected by Mr. Batty, 

 the Mexican form proves to be much duller colored, with the 

 flanks in the brightest specimens as obscurely colored as in 

 the very palest of the Chiriqui examples, none of them pre- 

 senting the golden rufous so characteristic of the latter. (See 

 below, p. 80.) The sides of the back are yellowish gray 

 washed with blackish, with the long hairs at the lower edge 

 of the flanks dull yellowish gray with dull brownish tips, 

 instead of rich golden with the tips almost golden chestnut. 



The young in first pelage are dull, dingy gray, varied slightly 

 with a wash of blackish, especially on the head, middle of the 

 back, limbs, and tail. 



19. Ateles pan Schlegel. Represented by 22 specimens, 

 mostly adult, but including a few young adults, and one in 

 first pelage, collected March 5 April 19. 



