258 Allen's naturalist's library. 



Among other peculiar skeletal characters may be mentioned 

 the schizognathoiis palate, the absence of basipterygoid pro- 

 cesses {cf. vol. i. p. T, fig. i), the shape of the dorsal ver- 

 tebrae and the sternum. The shape of the latter is unique, 

 the lateral edges being nearly parallel for about two-thirds of 

 their length, then diverging so that the sternum is wider pos- 

 teriorly than anteriorly. There are two small notches on either 

 side of the posterior margin, the outer being reduced to a 

 foramen. The kel of the sternum is very small, and cut 

 away in front with a flattened out and broadened surface at 

 the posterior termination. On this flattened surface the 

 greater part of the weight of the body is supported when 

 the bird is at rest. The bones of the shoulder girdle — the 

 coracoids, clavicles, and furcula — are completely joined (anchy- 

 losed) to one another and to the sternum. 



The crop is enormous, and occupies the upper part of the 

 chest, distorting the furcula and sternum ; it is placed in a 

 deep cavity in the upper half of the pectoral muscles. 



The hind toe, or hallux, is very long. 



The first secondary quill is not much shorter than the 

 second. 



The oil-gland is tufted. 



The young are hatched naked, the thumb and first finger 

 being provided with claws which enable them to climb and 

 grasp the branches soon after they are hatched ; the bill, as 

 well as the legs and wings, being used for a similar purpose. 

 They are able to swim and dive with facility, when compelled 

 to do so. 



The eggs are double-spotted and remarkably Rail-like. 



FAMILY OPISTHOCOMID^. 



THE HOATZINS. GENUS OPISTIIOCOMUS. 



Opisthocomits, IHiger, Prodr. Syst. Mamm. et Av. p. 239 



(1811). 



Type, O. hoazi?i (Miill). 



