MYOLOGY OF OPISTHOCOMUS CRISTATUS. 355 
prominent, and preserves the diameter of its ridge very uniformly throughout its length ; 
the pectorals are, also, of an equal thickness throughout the whole of their sternal 
attachments; and the crop disports itself awkwardly enough upon their superficial 
aspect and the receding furcular angle, more especially when moderately distended. 
The Opisthocomus illustrates a perfect crop and calyx-like receptacle; but the Pheasant 
only the former, its nidus being referred to a rugged and uncomfortable habitat. 
Probably the most remarkable feature in the sternum is the prominent tubercle 
(Pl. LXIII. 4) in which the distal extremity of the keel terminates. It appears as an 
ovoid surface, somewhat flattened, and projecting to a corresponding level with the 
superficial surface of the pectorals, the fibres of which it separates at this particular 
spot. It is only covered by the integument, which is condensed upon it and closely 
connected with it. In the bird undivested of its plumage it can be readily seen—the 
skin over the tubercle being destitute of feathers. The keel in front and behind the 
tubercle bevels off in an arcuate manner, the posterior border being inconsiderable in 
length. The pectorals adapt themselves toa nicety to the alternating width of the 
keel, throughout its extent. Section of the pectoral muscle shows its gradually in- 
creasing thickness from the furcula to the double angular distal bends of the muscle. 
Its proximal attachments are similar to those of the generality of birds, viz. to the 
whole length of the furculum, keel of the sternum, to the distal margin of the lateral 
half of the sternum, and also to its lateral shelving plate (external xiphoid process) 
external to the attachment of the second pectoral. The under or sternal surface of the 
great pectoral is channelled for the accommodation of the 2nd pectoral and its minor 
associate. The muscle undergoes considerable condensation at its distal extremity, 
immediately prior to its insertion into the delto-pectoral ridge of the humerus. At the 
latter point it has some tendinous fibres mingled, but sparingly, with the muscular. 
From the middle of the superficial aspect of the insertional fibres, a few detach 
themselves as a small wedge-shaped muscle, about } an inch long (PI. LXIV.); this 
speedily terminates in a slender tendon, and receives the anterior portion of the differen- 
tiated deltoid muscle. The conjoined tendon traverses the brachium as far as the lower 
end of the humerus, where it divides into two tendons: the anterior one is inserted into 
the tendon of origin of the extensor carpi radialis longior; and the posterior, smaller 
than the preceding, crosses the outer aspect of the extensor muscles, continues its course 
along the bases of the wing-feathers as a fascial expansion, and is finally lost upon the 
dorsal aspect of the carpus. This tendon gives slips of attachment to all the cubital 
feathers except the last three or four. 
There is another small muscle (Pl. LXIV. fig. 3) which arises from the fascia covering 
the biceps, immediately below the lower border of the great pectoral muscle. Its 
muscular belly is three quarters of an inch long, fusiform in shape, and ends in a slender 
tendon, which traverses the cubit as far as the base of the lst metacarpal. These 
muscles constitute the extensor plice alaris of Professor Owen’. 
1 Prof. Owen (Anat. & Phys. of Vert. vol. ii.) describes this extensor as consisting of “ two portions, of which 
3B2 
