THE SKELETON IN FISHES. THE RIBS. 



125 



todus and Lepidosiren have five, like most other fish. The 

 branchial arches bear gill rakers. 



....10 



.-11 



FIG. 19. DORSAL (TO THE LEFT) AND VENTRAL (TO THE RIGHT) VIEWS 

 OP THE CRANIUM OF Ceratoclus iiiiolepis (after GUNTHER). 



6. 



cartilaginous part of the 7. 



quadrate with which the 8. 



mandible articulates. 9. 



scleroparietal. 10. 



frontal. 11. 



ethmoid. 12. 



nares. 13. 



orbit. 14. 



pre-opercular (squamosal). 

 second rib. 

 first rib. 

 vomerine tooth, 

 palato-pterygoid tooth, 

 palato-pterygoid. 

 parasphenoid. 

 interopercular. 



RIBS. 



As has been already mentioned (p. 24), although ribs 

 commonly appear to be the cut-off ends of the transverse pro- 

 cesses, they are really elements derived from the ventral or 

 haemal arch. 



In Elasmobranchii and other cartilaginous fish they have 

 the form of small cartilaginous structures imperfectly separated 



