290 FISHE6. 



a slit in this situation, and another more in front between the two 

 frontals, &c. 



Upper Jaw. 



To recognize easily the intermaxillaries and the maxillaries , they 

 should be seen in the salmon, or in trouts properly so called.* In 

 such fishes, these bones are situated in Hie same manner as in all the 

 mammalia i nd reptiles ; the intermaxillaries (No. 17) on the front of 

 the jaw. having little mobility ; the maxillnrics (No. 18) at the sides as 

 far as the commissure, armed with teeth, which continue the series of 

 those of the intermaxillaries. On each side, within the maxillary 

 teeth, there is another series of teeth belonging to the palate, as in 

 serpents, and in the middle there is a band of them, adhering to the 

 longitudinal hone, which is, as we have remarked, analogous to the 

 vomer. This structure obtains in the smelts, the graylings or cor- 

 regoni, and throughout the entire family of the herrings. In the 

 polypteus, the resemblance to the mammalia and reptiles goes still 

 farther ; its maxillaries and intermaxillaries are immoveably attached 

 to the rest of the head. 



There are structures more or less analogous in other different kinds, 

 but in the greater number of fishes, as in the cyprins, and almost all 

 the acanthopterygians, the intermaxillary (No. 17) forms almost the 

 whole of the edge of the superior jaw, and is moved by causing one 

 ascending apophysis to glide before the anterior extremity of the 

 cranium, which extremity is formed, as we have said, by two bones 

 analogous to the ethmoid (No. 3,) and vomer (No. 16). The maxil- 

 lary (No. 18) is placed parallel to the intermaxillary, and forms what 

 is commonlv called the labiod bone* On account of its being sometimes 

 covered With a fold of skin representing a lip, or the mystachial bone, 

 from its representing a sort of moustache, and from this bone being 

 sometimes prolonged into a little fleshy barb or true moustache, as is 

 seen particularly in the silures. This maxillary bone (No. 18) is 

 joined by moveable articulations to the intermaxillary (No. 17), to a 

 prominent facet of the vomer (No. 16,) and to a slightly curved 

 apophysis of the palatine bone (No. 22.) It is thus that the inter- 

 maxillary, the maxillary and palatine bones, with the apparatus 

 attached to this last, are moved on each other, and on the cranium. 

 The maxillary (No. 18) is sometimes subdivided into two or three 

 pieces, as in the herrings, or even into a much greater number as in the 

 lepisi;steus. The ascending apophysis of the intermaxillary (No. 17) 

 is sometimes distinguished from the rest of its body by a suture :f an 



* These parts in the trout are represented pi. iii. fig. v. with the same numbers as 

 in the figures taken from the perch ; the entire face of the latter is represented in 

 situation, pi. iii. fig. i. and all the bones detached from each other fig. ii. 



t I thought for some time that the labial bone corresponded to the juiral. 

 M. Fischer seems to regard it in the same light in his treatise on the intermaxillary 

 bone, in which he considers the anterior extremity of the cranium as corresponding . 

 to the upper jaw. M. Rosenthal adopts the ideas of M. Fischer on this latter point, 

 but thinks that the labial is but a dismemberment of the intermaxillary. In 1811, 

 I recognized the labiai for what it really is, by observing it in the trouts, and I find 

 that this opinion has been since adopted by all the osteologists except M. Rosenthal. 

 It is, indeed, evident to any person who commences the; study of this bone in the 

 trout, and other species, in which it forms part of the edge of the jaw. 



