opisTiiocoMi. 523 



Order YIII. OPISTIIOCOMI. 



Palate scbizognathous ; nasals holorhinal ; no basyptcrygoid pro- 

 cess; antepenultimate dorsal vertebrae free, tbe inferior faces of 

 tlie centra of tbe dorsal vertebrae are flattened and without crests; 

 tbe sternum is unique — tbe lateral edges are nearly parallel for two 

 thirds of its length, then diverge so that it is wider posteriorly than 

 anteriorly ; the posterior margin with two small notches on each 

 side, the outer being reduced to a foramen ; keel very small and cut 

 away in front with a Hattened-out and broadened surface at the 

 posterior termination of the carina sterni. On this surface the 

 greater part of the weight of tbe body is supported when the bird is 

 at rest. The coracoids, clavicles, and furcula (which are short) are 

 completely ancbylosed to each other and to the sternum. 



Tlae enormous crop distorts the furcula and sternum and occupies 

 tbe upper part of the chest, being placed in a deep cavity in tbe 

 u])per half of the pectoral muscles. 

 Hallux very long. 

 Xo bastard secondary. 

 Oil-gland tufted. 



Xo lateral bare tracts on the neck ; the inferior feathered tracts 

 beginning at tbe bottom of the neck run in two parallel bands which 

 taper gradually towards the vent ; dorsal tract bifurcates between 

 the shoulders. 



Tbe youug are hatched naked, and the pollcx and index digit are 

 provided with a claw which enables them to climb soon after they 

 are hatched, the bill as well as tbe legs and wings being used for 

 holding on to the twi^s ; they are also able to swim and dive with 

 facility when compelled to do so. 



Eggs two or three in number, double-spotted and Eail-like. 

 Nest composed of sticks and placed on the tops of bushes near the 

 water's edge. 



Family I. OPISTIIOCOMID/E. 



1. OPISTHOCOMUS. 



Typo. 



Olii.-thocomus, lUiger, Prodr. Si/sf. Mamm. et Av. p. 239 



(1611) ; I''h»i. I'hil. ZooL ii. p. I'O-' (\f-2-2) 0. hoazin. 



Orthocorys, Vicill. Analyse, p. 4!) (16Iti) O. Loaziu. 



Siisa, Vieill. Nvuv. Diet. cfJlist. Xat. sxx. p. 216 (1819). 0. hoaziu. 



Tail elongate and rounded, composed of 10 feathers, the middle 



pair being considerably longer than tbe outer pair. 



