168 



ANATOMY OF VERTEBRATES. 



haps, also, the more posterior position of the heart in these Fishes. 

 In the Sharks and Chimaerae the arch is loosely suspended by 

 ligaments from the vertebral column : in the Rays the point of re- 

 sistance of their enormous pectoral fins has a firmer, but somewhat 

 anomalous attachment, by the medium of the coalesced upper ends 

 of the suprascapular pieces to the summits of the spines of the 

 confluent anterior portion of the thoracic abdominal vertebra?. In 

 the Sharks the scapular arch consists chiefly of the coracoid por- 

 tions, fig. 104, 52, which are confluent together beneath the peri- 

 cardium which they support and defend ; the scapular ends of the 

 arch, connected to the coracoids by ligament, project freely upward, 

 backward, and outward. To a posterior prominence of the cora- 

 coid cartilage corresponding with the anchylosed radius and ulna, 

 ib. 54, 55, in the Lophius, there are attached, in the Dog-fish and 

 most other Sharks, three sub- compressed,, sub-elongated carpal 



104 



Cartilages of the pectoral fin and arch of the Dog-fish (Spinax acanthias) 



cartilages, the uppermost, ib. 56, the smallest, and styliform ; it 

 supports the upper or outer phalangeal ray. The next bone, ib. se', 

 is the largest and triangular, attached by its apex to the arch, and 

 supporting by its base the majority of the phalanges. The third 

 carpal, ib. 56", is a smaller but triangular cartilage, and supports 

 six of the lower or radial phalanges. Three joints (metacarpal 

 and digital) complete each cartilaginous ray or representative 

 of the finger, ib. 57 ; and into the outer surface of the last are 

 inserted the fine horny rays or filaments, ib. 57 /x , the homologues 

 of the claws and nails of higher Vertebrata, but which on their first 

 appearance, in the present highly organised class of Fishes, mani- 



