108 OPISTHOCOMID^. 



Order OPISTHOCO MIFORME S. 



The eggs of Opisthocomus hoazin, the sole representative of the 

 Order, closely resemble the eggs of some of the Rails, especially 

 those of the Hypotcenidia group, and, like them, are double-spotted. 



Family OPISTHOCOMID^E. 



Genus OPISTHOCOMUS, lUiger. 



Opisthocomus hoazin (P. L. S. Mull). 



Opisthocomus cristatus, Newton, P. Z. S. 1867, p. 164, pi. xv. fig. 7 ; 



Cabanis, J. f. 0, 1870, p. 318, taf. i. fig. 3 ; Quelch, Ibis, 1890, 



p. 327. 

 Opisthocomus hoazin, Grant, Cat. Birds B. M. xxii. p. 524 (1893) ; 



Sharpe, Hand-l i. p. 93 (1899). 



The eggs of the Hoatzin are fairly smooth, have little or no gloss, 

 and vary in shape from the elliptical to the broad oval. They are 

 of a pinkish cream-colour, marked with dots, smears, and blotches 

 of pale lavender and reddish brown. The markings are generally 

 more thickly clustered at one end of the egg than elsewhere. 

 Specimens measure from 1-62 to T84 in length, and from 1-25 to 

 1-31 in breadth. 



5. Deinerara. J. J. Quelch, Esq. [P.]. 



2. British Guiana (J. J. Quelch). P. L. Sclater, Esq. [P.]. 



Order RALLIFORMES. 



The eggs of the Rails and Coots are for the most part double- 

 spotted, but many exceptions occur, some being plain white, and 

 others so densely marked with surface streaks and spots that no 

 traces of the underlying markings are visible. 



The texture of the shell is generally smooth, but many examples 

 exhibit a certain roughness. The amount of gloss is variable. 



Normally, the eggs of the Rails are of a regular oval form, but 

 those of some species are elliptical, biconical, or even spheroidal. 



