CLASS OF FISHES. 



375 



Such generally is the complicated structure of the head of 

 fishes : anomalies exist, as in the sword-fish and in some 

 species allied to the tunny; in these the upper jaw is pro- 

 longed into a powerful weapon, with which they attack the 

 largest sea animals. Any further comparison with the osseous 

 head of mammals need not detain us here, for much uncer- 

 tainty prevails. 



ph ar 



co ca ab h r b I 



Fig. 384. Head and Eespiratory Apparatus of a Fish.* 



479. In the vertebrate column there are hut two distinct 

 portions, a dorsal and a caudal (Fig. 382). The body of each 

 vertebra is formed like an hour-glass, with the two extremi- 

 ties hollowed out into conical cavities which sometimes unite 



* Fig. 384. Osseous head of the Perch, partially dissected, so as to show 

 the interior of the mouth and the hyoid apparatus : c, cranium ; or, orbit ; 

 v, vomer, armed Avith teeth; im, upper jaw ; dp, teeth fixed inro the pala- 

 tine arch; m, lower maxillary; , lingual bone; b, lateral branches of the 

 hyoid apparatus ; s, stylet serving to suspend these branches to the inner 

 surface of the jugal partitions ; r, radii branchiostegi ; a, branchial arches; 

 ph, superior pbaryngeal bones ; ar, articular surface of the partition already 

 mentioned ; o to h, osseous girdle supporting the pectoral fin (p) o and o , 

 scapula, formed of two pieces; h, humerus; ab, bones of the fore-arm ; ca, 

 carpal bones ; co, coracoid bone. 



