286 FISHES. 



To complete the posterior and superior lateral angle of the cranium, 

 one, and sometimes, two bones are always found, on each side, between 

 the posterior frontal, the frontal, the parietal, the internal occipital, 

 the lateral occipital and the great wing ; the first, (No. 12), is mani- 

 festly the same as that which I have called mastoidean in the croco- 

 dile and tortoise. f It contributes with the posterior frontal, and 

 sometimes with the great wing to form the articular surface of the first 

 bone of the palatine, and tympanic apparatus, that bone which I 

 have called the temporal. This mastoidean bone, in fishes, is pro- 

 longed into an apophysis more or less prominent, forming the summit 

 of what I call the external ridge of the cranium, and gives attachment 

 to one of the apophyses of the superior bone of the shoulder or supra- 

 scapular. 



When there are only two of these to complete the angle of the cra- 

 nium, a disposition which obtain almost always in the Acanthoptery- 

 gians, the only name I can find for the second, (No. 13) is that of 

 the petrous bone. It is in general small, and placed between 

 the mastoidean, the lateral occipital and the great wing ; sometimes 

 it is veiy large, and descends as low as the inferior occipital and the 

 sphenoid]: as in the cod ; it is also often entirely wanting, as in the 

 pike, carp, and eel. 



In front of the great wing, but somewhat higher, a piece (No. 14) 

 which may be called the orbitary wing is dove-tailed with the great 

 wing, and with the posterior frontal, and frontal.§ Between this 

 and its fellow, the olfactory nerves pass above, and the optic nerves 

 below ; they both unite, sometimes as in the carp, thus forming a roof 

 over the optic nerves. 



BeloAV, and in front of the orbitary wings, a single bone is found, 

 (No. 15), it is most commonly implanted by a solitary lamina on the 

 sphenoid, it bifurcates above to join, sometimes the two orbitary 

 wings, sometimes the two great wings, it also sometimes remains sus- 

 pended in the interorbitary membrane, Avhich unites all these parts ! 

 This is an anterior sphenoid, very analagous, as in the pike, to what 

 obtains in the lizards ;|| but sometimes as in the cyprins, and the sil- 

 ures, this bone is large, and is united not only to the sphenoid and or- 

 bitary wing, but to the frontal, and anterior frontal ; in this case, it 



t M. Geoffroy at present calls my mastoidean, the prerupeal, and my petrous bone, 

 the posfupeal, and considers both as parts of it. M. Spix regards it as the scaly 

 temporal, and a part of the lateral occipital. M. Bojanus gives them names, the 

 inverse of mine. M. Bakker thinks my mastoidean is the temporal. M. Meckel 

 alone agrees with me, in regarding it as a substitute for the mastoid apophyses. 



X It is the petrous bone of the eglefin which M. Bakker has taken for the great 

 wing of the sphenoid, of which it has in realify the appearance in the cod species. M. 

 Meckel points out this bone, but does not determine it. 



§ M. Geoffroy who has adopted my determination, call this piece ingrassial. M. 

 Rosenthal calls it simply the wing of the sphenoid. M. Meckel looks upon it as 

 the great wing. 



II According to M. Rosenthal, it is this bone that forms Me 6oc7^ of the spftenoirf; 

 according to M. Spix, it is the ethmoid. M. Meckel makes of it the orbitartf tcing. 

 M. GeofiFroy adopts my determination, and calls it the entosphenal bone. 



