NOCTURNAL RAPACIOUS BIRDS. 67 



over, the whole body, with the exception of the axillary cavity and the lateral neck-spaces, is 

 covered with true permanent down-feathers, which bear no evanescent tips. In these birds I 

 found no setiform tips on these nest-down-feathers, such as occur elsewhere, for example, in the 

 Cursorial Birds (see below, Chapter VI). 



II. NOCTURNAL RAPACIOUS BIRDS (Accipitrince nocturne). 



There are two points which essentially distinguish this group pterylographically from 

 the preceding, namely, the constant absence of the aftershaft and the want of the circlet 

 of feathers at the apex of the oil-gland. Besides this we may indicate, as a general 

 character of the Owls, the remarkable size of all the contour-feathers, and the consequent narrow- 

 ness of the tracts. In many places, especially on the two gular portions of the inferior tract, 

 these consist only of two rows of feathers, but usually, as on the dorsal part of the spinal tract, of 

 three rows, the feathers of which are placed alternately, so that every two feathers of the outer 

 rows form a quincunx with one of the middle ones. A larger number of rows usually occurs only 

 on the cervical band and the pectoral bands, in which there are generally Jive. Between these 

 feathers of the tracts the down-feathers are probably entirely wanting ; at least I always miss 

 them when I particularly look for them. In their form the tracts agree in general with those 

 of the Falcons, although they present noticeable differences. Among these the chief is that in the 

 Owls the region of the throat between the rami of the lower mandible is never continuously 

 feathered (see Plate II, figs. 8 and 11), but the inferior tract issues from the angle of the 

 gonys, in the form of a narrow band, and divides on the middle of the neck, or close to the 

 front of the furcula, but never emits an inner branch. The truncal stems of the inferior tract, 

 as in Circus, are placed very close to the crest of the sternum, then bent, separating more 

 from each other towards the ventral surface, and only meeting at the anus. The spinal tract also, 

 although arranged in accordance with the principal type of the Falcons, presents this difference 

 the two arms of the dorsal portion which run to the fork of the scapular portion consist, probably 

 always, of two rows of feathers. 



The differences of the species among themselves are shown in the following arrangement : 



I. Owls with the outer branch of the inferior tract free posteriorly. 



This form of the inferior tract, which is shown in Plate II. fig. 8, agrees perfectly with the 

 principal type of the Falcons ; even the hook springing from the extremity of the outer branch, 

 and running to the hypopterum, is usually present. The species belonging to this section are 

 again divisible into two groups, according to the arrangement of the scapular portion of the spinal 

 tract. 



A. With the scapular portion of the spinal tract forming a deeply divided fork. 



In this case the furcation reaches to the end of the neck, the true nape, and is always 

 connected by two slightly divergent, biserial bands of contour-feathers with the dorsal portion, 

 which is simple from the caudal pit. The dorsal portion is not merely continued to the oil-gland, 

 but surrounds this with its feathers. 



