436 



COLLEGE ZOOLOGY 



Ribs (Fig. 372, R) are attached by ligaments to the centra 

 or parapophyses of the abdominal vertebrae and serve as a pro- 

 tecting framework for the body-cavity and its contents. There 

 is no sternum. I ntermuscular bones (G) are also attached to 

 some of the vertebra?. In the caudal region hcemal arches and 

 hcsmal spines (uD) extend down from the centrum, and the 

 caudal artery and caudal vein pass through these arches. The 



$i 



*-~.v-.-- ,A^t"-*v>->* 



FIG. 372. Skeleton of perch. A., anal fin; An., orbit; B., ventral fin; 

 Be, pelvic bones; Br, pectoral fin; Fr, interspinous bones; Kd, parts of 

 operculum ; o, maxilla; oD, neural spines; R, ribs; Ri., ist dorsal fin; 

 R2., second dorsal fin; S, caudal fin; Sch, bones of shoulder girdle; u, man- 

 dible; uD, haemal spines; z, premaxilla. (From Schmeil.) 



extreme posterior portion of the vertebral column is modified 

 so as to furnish a support for the caudal fin (S) . 



The skull of the perch (Fig. 372) consists of a large number 

 of parts, some of bone, others of cartilage. As in Petromyzon, 

 these parts may be grouped into the cranium and the visceral 

 skeleton. The cranium is originally of cartilage, but becomes 

 strengthened by the addition of membrane bones, which are 

 dermal ossifications. The cranium protects and supports the 

 brain, auditory organs, and olfactory sacs, and furnishes orbits 

 (Au) for the eyes. 



