HOATZIN 



401 



Hoatzin. 



A very remarkable and primitive type of bird is the hoatzin 

 (Opisthocomus cristatus), whose affinities are still doubtful. It is 

 the only representative of its family, and noteworthy, among other peculiarities, 

 on account of the presence of claws on the first and second digits of the wings in 

 the young birds, by means of which they hold on to the branches or bark as they 

 climb in the trees. Among other peculiarities of this bird, it may be mentioned 

 that the crop is unique on account of having assumed the structure and function 



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MEXICAN CURASSOW. 



of the gizzard of other birds, being much larger than ordinary, with the walls 

 thick and muscular instead of thin and flabby. Despite this specialised feature, 

 the primitive character of the hoatzin is indicated by many points, the vestigial 

 claw of the third digit of the wine linking it with the extinct lizard-tailed bird 

 (Archceopteryx), while another claim to primitiveness is apparent in the quadrupedal 

 habits of the young. Thickly wooded river-valleys form the haunts of the hoatzin, 

 of which Lower Amazonia may be considered the centre, the distributional area, 

 according to our present information, being in several instances discontinuous. 

 The bird has a peculiarly disagreeable odour of its own, which is, however, less 

 vol. it. — 26 



