284 FISHES. 



The anterior frontals, fig. 2, form the pillar of the forepart, allowing 

 the olfactory nerves to pass hetween them, as in all the animals in 

 ■which these bones exist. The ethmoid, however, fig. 3, forming 

 at this point a vertical partition between which and the anterior 

 frontal, the nerve on either side passes by a slight fissure in the latter, 

 but very often through a hole in the anterior frontal, and not by a 

 fissure ; still, this bone is not the less capable of being recognised for 

 what it really is. In the conger and common eel it remains in a 

 permanent state of cartilage ; if the skeletons be too long macerated, 

 the bone will disappear. The anterior frontal has an articulating 

 surface on its inferior edge for the palatine, fig. 22, and frequently, on 

 the outside of the latter, another for the first suborbital fig. 19*. 



The posterior frontal, f. 4, forms the posterior pillar of the orbit, 

 and co-operates in supplying an articulation to a bone to which I 

 give the name of temporal, f. 23f. 



The axis of the inferior surface is occupied as usual by the basilar, f. 5. 

 and the sphenoid, f, 6. The latter bone is continued forward, as in the 

 birds, into a long apophysis which is the base of the interorbital 

 partition, this partition remaining in the greatest number of fishes, 

 membranous ^. 



Taking these elementary indications for our guide, we come to 

 conclusions which can be demonstrated very easily in other bones ; 

 but we also become acquainted with the fact that, as in the birds and 

 reptiles, their number is not the same as it is in the human foetus, and 

 ■what is more, we shall see that it is not constant either in the various 

 fishes. 



The two parietal bones may be easily distinguished behind the 



* M. Spix, in conformity -with his general system, takes the anterior frontal of 

 the fishes for a lachrymal, and M. Oken for an os planum. We have to apply to 

 these theories the very same objections as we have given in our asteology of the 

 crocodile in our work on Fossil Bones. In these animals this bone is situated 

 beside a cartilaginous ethmoid, which it envelopes, as the anterior part of the frontal 

 covers the ethmoid in tbe Ruminantia. M. Bojanus, no doubt taking into consider- 

 ation the aperture which he finds in several fishes for the olfactory nerve, makes of it 

 a sieve-like lamina from the ethmoid ; but this opinion, which has not the same 

 ground for support in the whole of the species, is overturned besides by the other 

 relations which this bone bears to the adjacent ones. Now, with respect to M. Ro- 

 senthal, who arranges it as a portion of the upper jaw, the only only way in which 

 I can explain his notion, is to suppose that he did not study the reptiles in which 

 the anterior frontal is actually detached wholly from the jaw by a lachrymal. M„ 

 Geoffroy and M. Cams, call this bone a lachrymal, as does M. Spix. M. Bakker 

 adopts my nomenclature, but he denominates the frontal bone the osbital. 



-f- Authors differ much on this posterior frontal. According to M. Bosenthal and 

 M. Bojanus, it is the scaly portion of the temporal ; to M. Spix it is a part of the 

 jugal ; to Bakker it is the pethous bone. M. Geoffroy takes up the notion of the 

 first two, and calls thrs bone the temporal. 



X Every body seems to be agreed respecting the posterior sphenoid, with the 

 exception of M. Geoffroy, who makes out in the first a transverse division which I 

 am utterly unable to detect. He calls the posterior and segment basisphenal, the 

 anterior ostosphenal ; and the sphenoid hyposphenal. M. Rosenthal gives to the 

 sphenoid the vain title of bone of the base of the cranium, (in the German grund- 

 bein). M. Meckel understands tbe reunion of the basilar, the sphenoid, and the 

 lateral bones which are attached to it. 



