OCCIPITAL SEGMENT, OR VERTEBRA. 41 



in which it supports an appendage in the form of a single 

 many-jointed ray, retaining the archetypal character, Fig. 

 7, No. 53. In other fishes, the number of rays progress- 

 ively increase, until, in those called " rays" par excellence^ 

 they exceed a hundred in number, and are of great 

 length, forming the chief and most conspicuous parts of 

 the fish. The more common condition of the appendage 

 in*question is that exhibited in the species figured. Cut 9. 

 So developed, it is called in ichthyology the " pectoral 

 fin :" otherwise and variously modified in higher animals, 

 the same part becomes a fore-leg, a wing, an arm, and 

 hand. Some of the special names, originally applied to 

 the parts of the scapular appendage in man, are retained 

 and applied to like parts in the pectoral fin of the fish. 

 Of the two flat bones connecting the fin with the coracoid, 

 the upper one is the " ulna," No. 54 ; the lower one the 

 " radius," No. 55 ; the row of short bones joined with 

 these are the "carpals," No. 56; the longer and more 

 slender many-jointed rays answer to the parts called 

 " metacarpals" and " phalanges" in the human hand. In 

 the salmon there is a bone answering to the arm-bone or 

 humerus, which is articulated to the middle of the back 

 part of the coracoid by a transversely elongated ex- 

 tremity. It is also expanded at the distal end, where it 

 articulates by cartilage with the ulna and radius. The 

 ulna is a semicircular plate of bone perforated in the 

 centre, and, besides its articulation with the humerus, the 

 radius, and the ulnar carpals and metacarpal ray, it also 

 directly joins the broad coracoid. The radius, after ex- 

 panding to unite with the humerus, the ulna, and the 

 radial carpals, sends a long and broad process downwards 

 and inwards, which is united by ligament with its fellow 

 and with the lower termination of the coracoid. A basis 



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