OSSEOUS SYSTEM. (Comp. Anat.) 
Fig. 441. 
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- 
_ Yation between the different pieces of the skele- 
_ ton, consequent on the permanently cartilaginous 
State of the osseous system in these tribes. 
The suborbital bones in Fishes (fig. 437, 
 & 8 8; g) form a kind of chain composed of a 
_ very variable number of pieces which surround 
_ the inferior and external margin of the orbit, 
 eovering 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 prenasal bones, Owen; (nasal bones, 
Cuy.) of a Fish (fig. 436, 20) are found 
in a situatior 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 
831 
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,¢,¢) 
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 cuirassés,” 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. 
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. 
