3 88 



MANUAL OF ZOOLOGY. 



The caudal vertebrae (fig. 162) have no marked transverse pro- 

 cesses ; but, in addition to the neural arches and spines, they 

 give off an inferior or hcemal arch below the body of the verte- 

 bra, and the haemal arches carry inferior spinous processes 

 (haemal spines). 



The ribs of a bony fish are attached to the transverse pro- 



I cesses, or to the bodies of the abdominal vertebrae, in the form 

 of slender curved bones which articulate with no more than 

 one vertebra each, and that only at a single point. Unlike Jhe_ 

 ribs of the higher Vertebrates, the ribs do not enclose a thoracic, 

 cavity, but are simply embedded in the muscles which bound 

 the abdomen. Usually each rib gives off a spine-like bone, 

 which is directed backwards amongst the muscles. Inferiorly 

 the extremities of the ribs are free, or are rarely united to 



Fig. 162. Skeleton of the common Perch (P erca fluviatilis) . p One of the pectoral 

 fins ; v One of the ventral fins ; a- Anal fin, supported upon interspinous bones (*') ; c 

 Caudal fin ; d First dorsal fin ; d' Second dorsal fin, both supported upon interspinous 

 bones ; i i Interspinous bones : r Ribs ; ^ Spinous processes of vertebrae ; h Haemal 

 processes of vertebrae. 



dermal ossifications in the middle line of the abdomen ; but 

 there is never any breast-bone or sternum properly so called. 



The only remaining bones connected with the skeleton of 

 the trunk are the so-called interspinous bones (fig. 162, / /). 

 These form a series of dagger-shaped bones, plunged in the 

 middle line of the body between the great lateral muscles 

 which make up the greater part of the body of a fish. The 

 internal ends or points of the interspinous bones are attached 

 by ligament to the spinous processes of the vertebrae ; whilst 

 to their outer ends are articulated the "rays" of the so-called 

 " median " fins, which will be hereafter described. As a rule, 

 there is only one interspinous bone to each spinous process, 

 but in the Flat-fishes (Sole, Turbot, &c.) there are two. 



