AV£S. 



yoke-footed genera. The species which possess cceca closely accord with the Cuculoides in 

 their anatomy, but all of them possess the accessory plume to the clothing feathers, in which 

 they differ from that group. We subdivide them into Trogonoides and Cypseloides. 



The Trogonoides consisting of the Trogons only, it will be sufficient to refer to the generic 

 head (p. 216). They have twelve tail-feathers. 



The Cypseloides have only ten. They divide into two tribes, which may be termed Parvi- 

 rostres, containing the family of Podargues and Moth-hunters, nocturnal sjiecies with great 

 cceca, and which lay mottled eggs ; and Tenuirostres, comprising the two distinct famihes of 

 the Swifts and Humming-birds, which have no cceca, and lay white eggs, the last-named 

 family differing remarkably from all the preceding Strepitores in having a complicated inferior 

 larynx, which character obtains throughout the next order, without a single known exception. 



Although the foregoing long series of groups, more or less subordinate, evince a decided 

 mutual affinity and tolerably regular successionship, to those who have practically studied 

 them, we have been unable to detect a single character that will apply to all, and the only one 

 which approximates to being general, consists in the lower larynx being provided with only 

 the sterno-tracheal pair of muscles, save in the single family of the Humming-birds : hence 

 these birds are unable to inflect the voice, and sing ; and they are generally very inferior in 

 intelligence and docility to the members of either of the three other orders with which we are 

 now engaged ; the Picoides and Hoopoes constituting the chief exceptions to this generalization. 

 Linnaeus obtained a glimpse of their distinctness from the Passerince, when he instituted his 

 ordinal divisions Piece and Passeres; but he fell into error in assigning a position among the 

 former to the Crows, which alone could have induced Cuvier to remark that he could discover 

 no distinctive character to separate the Piece and Passeres of his great predecessor. 



The series of Strepitores can accordingly be defined only by negative characters, derived 

 principally from comparison of them with the Passerince. Perhaps the most remarkable fact 

 connected with their anatomy, consists in the cceca being invariably either altogether absent, 

 or, if present, developed to a considerable but fixed size, which never varies ; this diversity 

 being found to exist in groups that are nearly allied, as in the Swifts and Moth-hunters, the 

 Kingfishers and Todies, &c. 



IV. Cantores, or the restricted Passerince. — It is impossible for a greater contrast to be 

 afforded than is furnished by this ordinal division and the preceding one. Although com- 

 prising many more species and received generic divisions than the three foregoing orders 

 collectively, there is absolutely no essential difference of structure perceptible throughout the 

 whole immense series ; the only differences consisting in the degrees of developement of parts 

 common to all : the pecuUar type of skeleton, digestive and vocal organs, &c. being invariably 

 one and the same, just as the Humming-bird or Parrot model is analogously varied, in a minor 

 degree. There are no subdivisions equivalent to those which have been indicated as families 

 even of the Strepitores, however the beak may vary in magnitude and form ; the most dissi- 

 milar beaks being often unaccompanied by other marked diversities, so that a dead specimen 

 deprived of its head, although at the first glance it might be referred with certainty to the 

 present order, could only in a few instances be assigned, even on anatomical examination, to 

 any particular group of it, and the plumage and style of colouring would even then afford the 

 surest indication of its affinities, in the great majority of cases. In the Strepitores, on the 

 contrary, any one organ, and very commonly a single ordinary clothing feather, would suffice 

 to indicate the very genus from which it had been taken : the varieties in the form of the 

 sternal apparatus may be cited as one illustration of the considerable diversities observable in 

 the whole structure of the Strepitores; whereas a single sternal apparatus (fig. 86, p. l/S), 

 we have deemed fully adequate to represent the form of this important portion of the skeleton 

 throughout the amazingly extensive series of the present division.* There are, in fact, no 



nal apparatus of i 



enera of Cantores are beautifully fij(ure<l in Mr. YarrcU's History of British Birds. 



