532 ANNUAL KEPORT SMITHSONIAN INSTITUTION, 1910. 



Brazil — Continued. 



Amazona inferior. Est. do Amazonias, Rio Jurua, von lhering (25). 



Santarem, Pelzen (33). 



Lower Rio Capim, Goeldi (21). 



Obidos, Sclater. 



Marajo Island, Rio Anabiju, Bingham. 



The lower Amazon may thus be considered as a center of distribu- 

 tion from which the birds have slowly extended northward into the 

 Guianas and the Orinoco region, northwest to Colombia, west to 

 Ecuador and Peru, southwest to Bolivia, and south to the various 

 tributaries of this greatest of rivers. Not one of these localities is 

 separated by a real watershed, and all are in communication with the 

 Amazon either by direct tributaries or by marshy itabos, or river 

 joiners. 



GENERAL APPEARANCE. 



As far as general appearance goes, the name " pheasant " is not far 

 amiss when applied to the hoatzin. It comes closest in general aspect 



to the chachalacas, but there is some- 

 thing strongly suggestive of a peacock, 

 especially in the carriage of the neck 

 and head. This is well shown in the 

 positions of some of the individuals in 

 plate 3. 



My descriptions are based on 15 adult 

 hoatzins from the following localities: 

 Ciudad Bolivar (9), Guarapiche (1), 

 Bogata (1), Bolivia (1), Peru (1), 

 Amazon ( 1 ) , Abary , British Guiana ( 1 ) . 

 There is apparently no distinguishing sexual character and re- 

 markably little variation in size. However, the bird which I col- 

 lected in the Guarapiche, although adult, is distinct from all the 

 others in color ; and if these characters should be found to be constant 

 in other individuals the birds in this isolated locality would form a 

 distinct subspecies. 



The beak of the hoatzin is peculiar in shape, and a better idea can 

 be obtained from the outline drawing than from the description 

 alone. The mandibles are deep and w r ide, the average measurements 

 of 15* specimens being as follows: culmen, 29 millimeters; depth of 

 mandibles at gape, 22 millimeters; width at gape, 19 millimeters. 

 The striking character of the mandible is the shortness of the gonys, 

 this being only about 9 millimeters, or one-fifth of the total length of 

 the mandibles. The mandibles are slatj' olive, lighter on the edges. 

 The nostrils are round and placed about midway between the eye and 

 the point of the beak. The sides of the head are almost bare, being 

 covered only with a very scanty growth of black, bristlelike feathers 

 on cheeks, ears, and lores. Two row r s of these function as ej^elashes. 



