OSSEOUS SYSTEM. (Coiwp. ANAT.) 



831 



Fix. 441. 



moveable cartilages of the nose of other Ver- 

 tebrata ossified and entering into the composi- 

 tion of the facial skeleton. 



Besides the suborbital chain of bones (g,g,g,g) 

 above mentioned as partially surrounding the 

 orbit, and which in the Gurnards and other 

 hard-cheeked Fishes cover the cheeks as with a 

 bony case, entitling them to the name applied 

 to them by Cuvier of " joues cuirasses," another 

 chain of bones called the supra-temporal is not 

 unfrequently met with, placed on each side, 

 over the interval that separates the external from 

 the middle prominent ridge, developed from 

 the exterior of the cranium so as, together with 

 these projections, to cover the articulation of 

 the supra-scapular bone (46). These bones are 

 evidently peculiar to Fishes, and, like the sub- 

 orbital, must be referred to the exoskeleton 

 and not deemed to belong properly to the 

 osseous system. In this light they will be con- 

 sidered in another place. 



Fig. 442. 



Skull of the Crocodile of the Nile. 



the most complicated condition of this portion 

 of the skeleton. The higher cartilaginous 

 Fishes, however, ( Chondropterygii,) form a 

 very remarkable exception ; for in the Rays 

 and Sharks the face is reduced to a very simple 

 condition, in consequence of the want of sepa- 

 ration between the different pieces of the skele- 

 ton, consequent on the permanently cartilaginous 

 state of the osseous system in these tribes. 



The sttliorbital bones in Fishes (Jig. 437, 

 g, g, g, g) form a kind of chain composed of a 

 very variable number of pieces which surround 

 the inferior and external margin of the orbit, 

 covering the muscles of the face instead of 

 giving attachment to them, a circumstance 

 which induced Cuvier to believe that they did 

 not normally belong to the series of facial bones. 

 They are doubtless referable to the exo-skeleton 

 or cuticular bones so largely developed in some 

 fishes, and in this light they will be considered 

 in another place. 



The pnenaml bones, Owen ; (nasal bones, 

 Cuv.) of a Fish (Jig. 436, 20) are found 

 in a situation very analogous to that which 

 they occupy in the higher Vertebrata. They 

 form the internal boundaries of the nasal cham- 

 ber, and articulate superiorly with the frontal 

 (1). These bones are regarded by Professor 

 Owen as being the representatives of the 



Section of Crocodile's skull. 



The palatine arch or osseous roof of the 

 mouth is composed of analogous bones in all 

 the different races of Vertebrata ; but in the 

 lower Vertebrata there are found in connection 

 with this region of the skeleton several pieces 

 that have no representatives in the higher 

 classes. 



