HOACrZIN 423 



at which Garrod subsequently arrived after closely examining and 

 dissecting specimens preserved in spirit ; but the latter has gone 

 further and endeavoured to trace more particularly the descent of 

 this peculiar form and some others, remarking that the ancestor of 

 Opistlwcomus must have left the parent stem very shortly before the 

 true Giillinx first appeared, and at about the same time as the inde- 

 pendent pedigree of the Cuculidai and Mnsophagidse commenced — 

 these two groups being, he believed, very closely related, and 

 Opisthocoiims serving to fill the gap between them. Still more 

 recently Dr. Gadow has shewn that the very singular modification 

 of the sternal structure in this form is chiefly due to the extra- 

 vagant enlargement of its crop. 



It would be impossible here to state at length the facts on 

 which these vieAvs are grounded, and equally impossible to give 

 more than a very few details of the anatomy of this singular form. 

 The first thing that strikes the spectator of its skeleton is the 

 extraordinary structure of the sternal apparatus, which is wholly 

 unlilce that of any other bird known. The keel is only developed 

 on the posterior part of the sternum — the fore part being aborted, 

 or, as it were, cut away, while the short furcula at its symphysis 

 meets the manubrium, with which it is firmly consolidated by means 

 of a prolonged and straight hypocleidium, and anteriorly ossifies 

 with the coracoids. This unique arrangement seems to be corre- 

 lated with the enormously capacious crop, which rests upon the 

 furcula and fore part of the sternum, and is also received in a cavity 

 formed on the surface of each of the great pectoral muscles. Further- 

 more this crop is extremely muscular, so as more to resemble a 

 gizzard, and consists of two portions divided by a partial constric- 

 tion, after a fashion of which no other example is known among 

 birds. 



The Hoactzin appears to be about the size of a small Pheasant, 

 but is really a much smaller bird. The beak is strong, curiously 

 denticulated along the margin of the maxilla near the base, and is 

 beset by diverging bristles. The eyes, placed in the middle of a 

 patch of bare skin, are furnished with bristly lashes, resembling 

 those of Hornbills and some few other birds. The head bears a 

 long pendent crest of loose yellowish feathers. The body is olive- 

 coloured, varied with white above, and beneath is of a dull bay. 

 The wings are short and rounded. The tail is long, and tipped 

 with yellow. The legs are long, the feet stout, the tarsi reticulated, 

 and the toes scutellated ; the claws long and slightly curved. 

 According to all who have observed the habits of this bird, it lives 

 in bands on the lower trees and bushes bordering the streams and 

 lagoons, seldom taking wing, and then flying weakly, feeding on 

 leaves and various wild fruits, especially, says the late Mr. Bates 

 {Nat. Amaz. i. p. 120), on those of a species of Psidium, and it is 



