FISHES. 1 7 



unites beneath with that of the opposite side. Each half of this 

 belt, which in osseous fishes is situated behind the gill-cover, 

 consists of two pieces at the least. The uppermost is usually re- 

 garded as a scapula; in most fishes it consists of two divisions, one 

 placed below the other, of which the uppermost is situated like a 

 scaly plate at the side of the head, and begins with two arms. 

 The lower was by CuviER compared with the upper arm-bone 

 (humerus), but seems rather, as most writers conclude, to correspond 

 to the clavicle (according to Owen to the coracoid clavicle). Most 

 anatomists are of opinion that the coracoid bone in the osseous 

 fishes is represented by one or two bones, of which the lowest has 

 the form of a pointed osseous style ; this bone, or the uppermost 

 when there are two, is attached to the upper extremity of the above- 

 named osseous belt, and its lowest point, or the second bone, pene- 

 trates obliquely backwards and downwards amongst the muscles'. 

 Downwards are attached to the posterior margin of the osseous belt 

 two, seldom three, small bony laminae. The two, Avhicli are usually 

 present, may be regarded as the representatives of the bones of the 

 fore-arm {^radius and ulna) ; the third is probably a rudimentary 

 upper arm-bone {humerus), which, however, as a rule, aj)pears to be 

 wanting in fishes. 



To the outer extremity of the two bony plates, compared to 

 the radius and ulna, a row of four or five cylindrical or doubly- 

 conical small bones is attached corresponding to the carjjus. To 

 these no metacarpal bones are attached 2, but they sustain imme- 

 diately the rays of the pectoral fins, which may thus be compared 

 with fingers, but usually their number far exceeds that of the 

 carpal bones. 



The ventral fins are attached to a triangular bone with the point 

 directed forwards, which meets that of the opposite side in the 

 mid-line of the abdomen, the two being almost always connected 

 by suture. This bone represents the pelvis. Besides this, the 



^ Os epicoracoidewn of Owen corresponding with the clavicle. Here Owen recog- 

 nises the homologue of an inferior vertebral arch (kcemapophysis) belonging to the first 

 vertebi-a. Lectures, 1. 1. pp, 123, 160. 



2 In Polypterus alone there is a row of small bones, which may be compared with 

 the metacarpus, inserted between the carpus and the fin-rays, as also in the posterior 

 limbs between the pelvic bones and the rays of the fins there lies a row of four long 

 opicles, which might be named metat-arsal bones. Compare on the pectoral fins 

 C. Mettenheimer, Disquisitiones de Memhro Piscium pectoral?. 



VOL. II. 2 



