THE SKULL OF OSSEOUS FISHES. 99 



The palatine bones abut against the expanded anterior part of the 

 vomer, the under side of which commonly supports teeth. The left 

 ala of the anterior end of the vomer is chiefly developed in the 

 Ilolibut and other flat fishes. In the Lepidosteus, the vomer is 

 divided into two by a median cleft. Although its posterior end 

 joins obliquely to the under part of the pre-sphenoid, it is not, 

 therefore, less a continuation of tlie basi-cranial series than is the 

 post-sphenoid, which joins in a similar manner with the basi -occi- 

 pital.* In the Lepidosii'en, we have seen the basi-sphenoid confluent 

 with the basi-occipital ; in the Polypterus it is confluent with the 

 vomer. 



The prefrontals (neurapophyses of the nasal vertebra, ih. 14) 

 defend and support the olfactory prolongations of the cerebral 

 axis, give jiassage to these so-called ' olfactory nerves,' bound tlic 

 orbits anteriorly, form the surface of attachment or suspension for the 

 palatine bones, and through these for the palato-maxillaiy arch : 

 they rest below upon the pre-sphenoid and vomer, support above the 

 fore part of the frontal and the back part of the nasal bones, and 

 give attachment to the large antorbital or lachrymal scale-bone, when 

 this exists : they are always ossified in and from pre-existing cranial 

 cartilage. 



Such are the essential characters of the bones which Cuvier has 

 called ' frontaux anterieures 'f in Fishes, and to which I shall apply 

 the name of ' prefrontal ' in all classes of Vertebrate animals. In 

 the Cyprinoids, and most Halecoids, the prefrontals form part of an 

 interorbital septum. When anchylosis begins to prevail in the cra- 

 nial bones of Fishes, the prefrontals manifest their essential relation- 

 ship to the vomerine and nasal bones by becoming confluent witli 

 them: thus we recognise the prefrontals in the confluent parts of the 

 nasal vertebra of the Conger, by the external groove conducting the 

 olfactory nerves to the nasal capsules, and by the inferior process 



* Straus, however, argues it to be an appendnge from that mode of union 

 (xxxvi. t. i. p. 333.). 



f " Deux frontaux anterieures, qui donncnt passage aux nerfs olfactifs, ferment 

 les orbites en avant, s'appu3-ent sur le sjihenoiile ct Ic vomer, ct tlonnent attache par 

 une facette de leur horde inferieure aux palatins." {Lcgons cTAnat. Comp. ii. 1837, 

 1). C06.) Compare this enunciation of tlie essential characters of tlie anterior fron- 

 tals with Cuvier's descriptions of tlie l)oncs to which he applies that name in other 

 classes, and with the variable determinations of the same bones by other anatomists 

 — h hicrymal, Geoffroy and Spix ; lumina cribrosa ossis ethmoidei of Bojanus ; 

 sciUiche re'ichbeitie, Meckel, Wagner. Without at present entering into the respec- 

 tive merits or demerits of these determinations, I shall only state that the pre- 

 frontals, under wliatever names they are described, arc essentially the neurapoi)hyses 

 of the nasal vertebra, and that the failure in the attempt to determine the special 

 homologies of these bones may, in every case, be traced to the non-ajiprcciation of 

 their true general homology. 



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