496 



FISHES. 



Skin. 



The small scales which cover the body are developed in 

 the dermis, and are without any bone cells. Their free 

 margin is even, a characteristic to which the term cycloid is 

 applied, in contrast to ctenoid, which describes those scales 

 which have a notched or comb-like free margin. Over the 

 scales extends a delicate partially pigmented epidermis. 



Appendages. 



The pectoral fins are attached to the shoulder girdle just 

 behind the branchial aperture. The pelvic or ventral fins, 

 attached to what is at most a rudiment of the pelvic girdle, 

 lie below and slightly in front of the pectorals far from the 

 normal position of hind limbs. 



FIG. 165. External characters of a Teleostean a carp. 

 (After LEUNIS.) 



R., Dorsal unpaired fin ; S^., homocercal caudal fin : A., anal fin ; 

 B.B.) Pectoral and pelvic paired fins. Note also the lateral line and 

 barbule. 



Muscular System. 



The main muscles of the body are disposed in segments, 

 myotomes or myomeres, separated by partitions of con- 

 nective tissue. 



Skeleton. 



The Vertebral column consists of biconcave or amphi- 

 ccelous bony vertebrae. Each centrum in the trunk region 

 bears superior neural processes, uniting in a neural arch 

 crowned by a neural spine, and transverse processes pro- 



