28 PTERYLOGRAPHY. 



Plate IV, fig. 3), or true gap (Ardea stdlaris, Plate VIII, fig. 10, Scopus umbrella, Plate IX, 

 fig. 3), situated either at the end of the gular portion, or at the commencement of the branch 

 (for example, in Gypaclos barbatus, Plate II, fig. 1). 



I have observed the following principal forms in the ventral tract : 



1. Without an external branch, sparsely feathered, divided, even on the throat, by a narrow 

 space into a right and left band, each of which, instead of emitting a branch, becomes greatly 

 dilated upon the breast, is then suddenly narrowed at the region of the knee, and afterwards remains 

 of the same width. A ventral tract of this kind occurs in some Diurnal Rapacious birds, such as 

 Gypaetos (Plate II, fig. 1), Falco ccaudatus, DAUD., in which there is an inner or gular branch, 

 and all the Vultures, in which, however, on account of the nakedness of the neck, the gular 

 portion is wanting, except in Neophron, in which it is nearly complete ; also the genera Buceros 

 (Plate VI, fig. 1), Poyonias (sulcirostris, Plate V, fig. 6), Ciconia, and the other Pclargi (Plate 

 IX), PJtcenicoptcrus (Plate IX, fig. 6), and Fulica (Plate VIII, fig. 8). In GaUinula cMoropus we 

 meet with a similar structure, but the pectoral band is narrower, and exhibits a trace of a 

 branch. 



2. Like the preceding, broad or very broad ; but the truncal portion gives off a short branch 

 in the region in front of the knee-covert, and is not much narrower behind the latter. Examples 

 of this peculiar form are presented by Procellaria (ylacialis, Plate X, fig. 1, and capensis], 

 Puffinus (obscurus), Diomedea, in which the band is very broad, and the emargination behind the 

 branch deep ; likewise by the Unyuirostres (Plate X), in which this tract is widest, and scarcely 

 divided, but the emargination is inconspicuous. 



3. Without a branch, very broad throughout, scarcely separated at the neck, divided by a 

 narrow ventral space only at the upper part of the breast. I find the ventral tract thus 

 constituted in Dysporus (Plate X, fig. 8) and the other Steganojwdes. 



4. Without a branch ; distinct and divided, even on the throat ; broader on the breast, but 

 without any sudden external dilatation ; gradually narrowed posteriorly. It appears in this form 

 in Cypselus and Trochilus (Plate III), and is similar in the true Cuculina and in Ptcrocles, 

 although in these it is broader on the breast, and has the inner margin weakened. 



5. Without a branch ; first distinguishable on the breast (the plumage of the neck being 

 uninterrupted), and then divided into a right and left band, both of which are very broad at 

 the commencement, and gradually diminish backwards, without any indication of a branch or 

 separated dilatatipn. I found it in this form in Opistliocomus crislalus. 



6. Without a branch, and very anomalous, namely, combined on the neck and fore part of 

 the breast to form an uninterrupted plumage, but divided, on the breast, into four bands, which 

 run down to the tail, and enclose three spaces (one in the middle and one on each side near it). 

 The outer bands are dilated externally on the breast as far as the knee-covert, and then narrowed ; 

 the inner bands, on the contrary, are linear throughout, and narrower than the outer ones. I 

 have met with this truly singular arrangement in Otis tarda (Plate VIII, fig. 1) and similar 

 species; in Otis tetrax, on the 'other hand, the inner bands are much weakened, sparsely 

 feathered, and imperfect, or divided again. 



7. With an indistinct branch, narrow, and commencing on the throat, but divided by a 

 median space, which is particularly broad on the breast and belly ; the lateral branch projecting 

 but little, if at all, and only at the end, where it is abruptly truncated. A ventral tract of this 

 kind is presented by the Passerines (Plate III) and the genera Plioenicophanes (viridin/fas), 



