222 AVES. 
yoke-footed genera. The species which possess coeca 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 species with great 
coeca, and which lay mottled eggs ; and Tenuirostres, comprising the two distinct families of 
the Swifts and Humming-birds, which have no coeca, 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 j 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 Ploopoes constituting the chief exceptions to this generalization. 
Linnaeus obtained a glimpse of their distinctness from the Passerinee, when he instituted his 
ordinal divisions Pic(B and Passeresj 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 Passerinee. Perhaps the most remarkable fact 
connected with their anatomy, consists in the coeca being invariably either altogether absent, 
or, if present, developed to a cor iderable 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 Passerinee. — 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 
wdiole immense series ; the only differences consisting in the degrees of developement of parts 
common to all : the peculiar 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 i 
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; M'hereas a single sternal apparatus (fig. 86, p. 1/8), 
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 
* Tlie sternal apparatus of numerous genera of Cantores are beautifully figured in Mr. Yarrell’s History of British Birds. 
