ANATOMY OF VERTEBRATES. 103 



Protoptcri, as in more piscine Hamatocrya, the coracoid ex- 

 clnsively sujiports the appendage or limb. 



From the condition exemplified in fig. 101, A, the developement 



101 



Elementary limbs, .1. c, Lcpldc. siren ; n, d, Ami'iiiumn, r\r,. 



of the pectoral member diverges in two directions : one by multi- 

 plication of many-jointed rays, the other by simplification as to 

 number of rays and joints, with special modification and differen- 

 tiation of the latter. 



§ 39. Pectoral limb of Fishes. — The first series of modifications 

 is now confined to Fishes : but, before describing the appendage, 

 a brief notice of the arch is requisite. 



In most Osseous Fishes the pleura jjophy sis of the occipital, like 

 that of the two antecedent cranial vertebras, is in more than one 

 piece ; but the divisions do not exceed two. The U2:iper piece 

 (^suprascapula) is commonly bifurcate, as in the Cod, figs. 34, 75, 

 81, 50, the lower prong answering to the 'head,' the upper one to 

 the ' tubercle ' of the thoracic rib in the Crocodile : the latter 

 articulates with the transverse process {par occipital). The lower 

 piece {scapula), ib. 5i, is 'a slender straight bone, pointed below, 

 and mortised into a groove of the coracoid, ib. 52. The two parts 

 of the scapula are confluent in the Siluroid Fishes. In the 

 Murainoids the suprascajjula is ligamentous, and loosely appends 

 the scapular arch to the skull. In the Plagiostomi the arch is 

 detached from its vertebra, and has receded in position, to allow, 

 as it seems, for the great expanse of the appended fin. 



The hffimapophysis, or ' coracoid,' figs. 34, 38, 39, 75, 85, 52, is 

 lono-er and usually broader than the scapula. In the Cod-tribe, 



