and Classification of Birds. 317 



Tongue vermiform and protrusile: intestine of mean length. Sternum 

 doubly emarginated. Ex. Picidoe, in part; woodpeckers, piculets and wry- 

 necks. The tongue not protrusile. Ex. Picidce, the remainder; or the 

 honey-guides, (Indicator). With only ten tail-feathers. Ex. Bucconidcc ; 

 barbets. 



Feet zygodactyle, but on a different principle from the others ; the ordi- 

 nary inner toe being reversed. Cceca developed. Twelve tail-feathers. — 

 Ex. Trogonidce ; trogons. 



First and fourth toes disposed laterally. Ex. Tamatiadce ; or the puff- 

 birds, (Tamatia and Lyporynx), the barbacous, (Monasa), and the courols, 

 (Leptosomus). None of the remaining genera have more than ten tail-fea 

 thers. 



Feet zygodactyle, the outer toe reversed. Only eight tail-feathers. Ex. 

 Crotophagidce ; anis. With ten tail-feathers. Ex. Cuculidce ; cuckoos, 

 couas, coucals, and malkohas ; which should perhaps range in two or more 

 separate families* 



Feet ccenodactyle, but the outer toes separate to the articulation. Ex. 

 Podargidce ; podargues. Having the thumb directed inward. Ex. Capri- 

 mulgidce ; moth-hunters. 



The four toes directed forward. No cceca, nor posterior emargination to 

 the sternum. Ex. Cypselidce, in part ; the swifts, (Cypselus). With cceno- 

 dactyle feet. Ex. Cypselidce, the remainder; (Chcetura). The minute and 

 narrow tongue of the swifts and moth-hunters much lengthened and protru- 

 sile. Ex. Trochilidce ; humming-birds. 



(N.B. — The swifts and humming-birds are very intimately allied in their 

 whole structure ; but of this hereafter). 



The foregoing brief enumeration of some of the principal 

 distinctive characters of these various groups, will suffice to 

 shew that the yoke-footed birds cannot, with any propriety, 

 be ranged together as a single separate division. 



As in the Rapaces, so in the Heterogenes, the moult proba- 

 bly takes place in no instance more than once in a year ; and the 

 majority shed all their nestling feathers a few weeks after leav- 

 ing the nest. Others undergo no change till their second au- 

 tumn. 



The eggs, in by far the greater number of instances, are 

 pure white ; and most commonly deposited in holes of some 

 description. With few exceptions, the young are hatched 

 naked ; but in the moth-hunters, (and perhaps in the swifts), 

 are densely clothed with down from their first exclusion. 



A few are destitute of any gall-bladder, as the toucans, par- 

 rots, and cuckoos : in the touracos this organ is very small. 



The sternal apparatus presents very considerable modifica- 

 tion ; the entire group of Cantrices appearing to be equiva- 



*In Cuculus, and in Caprimulgus, the sterna are singly emarginated, and 

 not very unlike. The malkohas, coucals, and at least the true Coceyzi, (those 

 of Africa), are stated by L'Herminicr to have doubly notched sterna. I am. 

 quite ignorant of those of Crotophaga and Podargus. 



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