(>'l ORGANS OF SUPPORT, 



The detached condition of the bones of the head is most 

 remarkable in those of the anterior part of the face, 

 where the palatine bones ( 22, ) extending longitudinally 

 on the sides of the mouth, and often covered with teeth, 

 as in serpents, are freely moveable. The superior maxilla- 

 ries (18,) extending downwards laterally behind the inter- 

 maxillaries (17,) on each side of the face, are loosely ar- 

 ticulated to the vomer (16',) and to the palatine bones, 

 and are freely moveable in the osseous fishes, as are 

 also the intennaxillaries ( 1 7,) which bound the fore part 

 of the upper jaw. The lower jaw is generally composed 

 of at least two pieces on each side, the dental portion 

 (34,) in front containing the teeth, and the articular portion 

 (35,) behind connected with the head by a tympanic bone, 

 (below 27,) considered by Cuvier as the jugal. Fishes 

 have teeth implanted in almost every bone around the 

 interior of the mouth, in the intermaxillary, superior and 

 inferior maxillary bones, on the branchial arches, pharyn- 

 geal bones, palatine bones, os hyoides, and on the tongue 

 itself. The teeth are almost entirely osseous, without 

 fangs, and without alveoli ; irregular in size and position, 

 generally recurved spines placed in numerous rows, and 

 they often become anchylosed to the bones which sup- 

 port them. Their soft osseous texture, their thin cover- 

 ing of enamel, and their feeble attachment, correspond 

 with the soft condition and the imperfect union of the 

 bones which support these prehensile teeth, as we see 

 also in amphibia and serpents. Where the bones of the 

 head, which support them, are strong, and firmly united, 

 as in crocodilian reptiles and mammalia, the teeth are more 

 dense, covered with a thicker layer of enamel, provided 

 with fangs, and lodged in deep alveoli. Behind the 

 lower jaw is placed the operculum, consisting of a large 

 opercular bone (28,) a sub-opercular bone (32,) an inter- 

 opercular bone (33,) and often an additional small piece 

 below the sub-opercular. As fishes have no tympanic 

 cavity of the ear to confine their ossicula auditus, the 

 opercular bone is considered as an enlarged stapes, the 

 sub-opercular bone as the os orbiculare, the inter-oper- 

 cular as the malleus,, and the fourth small bone as the 

 iocus. These are placed behind the pre-opercular bone, (30,) 



