468 MANUAL OF ZOOLOGY. 



The fore-limb possesses in a modified form most of the 

 bones which are present in the higher Vertebrata. The 

 humerus, or bone of the upper arm, is usually wanting, or it is 

 altogether rudimentary. A radius and ulna (fig. 251, r, u) are 

 usually present, and are followed by a variable number of 

 bones, which represent the carpus, and some of which some- 

 times articulate directly with the coracoid. The carpus is fol- 

 lowed by the " rays " of the fin proper, these representing the 

 metacarpal bones and phalanges. The pectoral fins vary much 

 in size and in other characters. In the Flying Gurnard (Dac- 

 tylopterus], and the true Flying Fish (Exoccztus), the pectorals 

 are enormously developed, and enable the fish to take exten- 

 sive leaps out of the water. 



The hind-limbs or " ventral fins " are wanting in many fishes, 

 and they are less developed and less fixed in position than are 

 the pectoral fins. In the ventral fins no representatives of the 

 tarsus, tibia and fibula, or femur, are ever developed. The 

 rays of the ventral fins representing the metatarsus and the 

 phalanges of the toes unite directly with a pelvic arch, which 

 is composed of two sub-triangular bones, united in the middle 

 line and believed to represent the ischia. The imperfect pelvic 

 arch, thus constituted, is never united to the vertebral column 

 in any fish. In those fishes in which the ventral fins are 

 " abdominal " in position (/. ., placed near the hinder end of 

 the body) the pelvic arch is suspended freely amongst the 



Fig. 252. Outline of a fish (Perca granulate?) , showing the paired and unpaired fins. 

 /> One of the pectoral fins ; v One of the ventral fins ; d First dorsal fin ; d' Second 

 dorsal fin ; a Anal fin ; c Caudal fin. 



muscles. In those in which the ventral fins are " thoracic " or 

 "jugular" (i.e., placed beneath the pectoral fins, or on the 

 sides of the neck), the pelvic arch is attached to the coracoid 



