466 



MANUAL OF ZOOLOGY. 



bones, placed one behind the other, and termed by Owen the " basibran- 

 chial bones." Springing from these are four bony arches the "branchial 

 arches "which proceed upwards to be connected superiorly by ligament 

 with the under surface of the skull. The branchial arches as will be sub- 

 sequently described carry the branchiae, and each is composed of two 

 main pieces, termed respectively the " cerato - branchial " and " epi- 



-. 6 



Fig. 250. Os hyoides, branchiostegal rays, and scapular arch of the Perch (after 

 Cuvier). ss Supra-scapula ; s Scapula ; co Coracoid ; cl Supposed representative of 

 the clavicle ; a Glossohyal bone ; b Basihyal ; c Urohyal ; d Ceratohyal ; e Epihyal ; 

 f Stylohyal ; br Branchial arches ; t Branchiostegal rays. 



branchial " bones. The second and third arches are connected with the 

 skull by the intervention of two small bones, often called the ' ' superior 

 pharyngeal bones," but termed by Owen the " pharyngo - branchial " 

 bones. 



The limbs of fishes depart considerably from the typical form 

 exhibited in the higher Vertebrates. One or both pairs of 

 limbs may be wanting, but when present the limbs are almost 

 always in the form ofjfins that is, of expansions of the integu- 

 ment strengthened by bony or cartilaginous fin -rays. The 

 anterior limbs are known as the pectoral fins, and the posterior 

 as the ventral fins ; and they are at once distinguished from the 



