230 ME. W. p. PYCEAFT ON THE 



feathers. It is bounded on either side and in front by an aptevium. The remainder of 

 the interramal area lies behind the convergent ends of the peripheral disc-feathers, but 

 is almost directly lost in the pteryla colli ventralis (PL 25. fig. 2). It forms a narrow 

 tract of some two feathers in width. In one case, however, this expanded to merge on 

 either side with the mandibular area. 



The facial disc is formed by the feathers of the opercular and loreal areas afl.d those of 

 the postaural fold. These last form the periphery of the disc. 



Ft. colli dorsalis (PL 25. fig- 3). — A densely -feathered tract, not closely investing 

 the neck, but seated upon extensive lateral folds of skin, forming the T-shaped expansion 

 of a vertical median membrane. The tract is widest a little below its origin at the 

 occiput, then suddenly contracting, so that, at the point where it emerges with the 

 pf. s])in(ilis, it is reduced to an obliquely-transverse row of some 5 feathers. A membra- 

 nous fold investing a retractor muscle runs from the underside of the lateral neck- 

 membrane at a point a little below its greatest width, in an obliquely-downward direction, 

 to the pt. colli ventralis, and thence to the shoulder (PL 25. fig. 2). 



Ft. spinalis (PL 25. fig. 1}. — It is not pos.sible to draw a hard-and-fast line separating 

 this at its upper end from the i^t- colli dorsalis. It is divided into aa upper A-sliaped 

 and a lower Y-shaped portion. The former will henceforth be called the interscapular 

 fork, and the latter the lumbar fork. The arms of the interscapular fork arise in the 

 upper third of the interscapular region — iu one sj)eciinen at the root of the neck, where 

 it took origin from the pt. colli dorsalis, there being no stem — and terminate on a level 

 with the free end of the scapula. The feathers are seated in obliquely-transverse rows of 

 not more than 4 feathers in each row. The branches of the lumbar fork are wide apart 

 and continued upwards on to that portion of the axillary membrane lying between the 

 humeral tract and the arms of the interscapular fork. A double row of semiplumous 

 feathers enters into the formation of each branch, and these converge into the common 

 stem some distance in front of a line drawn through the acetabular region. The stem is 

 made up of transverse rows of feathers arranged in triplets (thus — . * .). It is bifurcated 

 posteriorly, terminating just in front of the oil-gland, after somewhat increasiug in 

 width. 



Pt. caudcv. — There are 12 rectrices. 



Ft. colli ventralis. — This comes into existence in the form of a backward coutinuation 

 of the interramal tract. At first made up of a treble (transverse) row of feathers, it 

 gradually increases in width to the middle of the neck, where it forks, each branch rimning 

 to join the pt. ventralis at the shoulder. 



Ft. ventralis (PL 25. fig- 3). — Three branches mu.st be recognized in this tract — an 

 outer, a median, and an inner. The outer is very distinct and runs backwards from the 

 shoulder across the pectoral muscles to the preaxial border of the patagium. The median 

 and widest of the three arises at the shoulder and runs backwards to within a short 

 distance of the level of the posterior border of the sternum ; here it turns abruptly 

 upwards and forwards to join the hypopteron. This upw^ard limb is the "hook" of 

 Nitzsch. The area between the hook aud its main stem is more or less thickly 



