40 



The postfrontals (it, 11) belong to the same category of vertebral pieces as the mastoids, 

 whose prominent crest they partly underlie and complete in the natural skull, lending their 

 aid in the formation of the single articular cavity for the tympanic pedicle. Like the mas- 

 toids their inner surface is expanded, and enters into the formation of the otocranial cavity : 

 they form the posterior boundary of the orbit ; are articulated below to the orbitosphenoid 

 and alisphenoid, above to the frontal, and by their posterior and upper surfaces to the 

 mastoid. 



The upper or neural arch of the segment which completes the skull anteriorly, consists of 

 the 'vomer' (13) below, the ' prefrontals ' (14) laterally, and the 'nasal' (is) above. 



The vomer (is) is thick and expanded anteriorly, slender and terminating in a point poste- 

 riorly, where it was wedged into the under part of the presphenoid ; its antero-lateral angles 

 were articulated to the prefrontals ; its upper surface supported the nasal bone by an inter- 

 vening cartilage. The palatine bones abutted against the expanded anterior part of the 

 vomer, the under side of which supports teeth. 



The prefrontals (14) rested below upon the prespheuoid and vomer, supported above the 

 fore-part of the frontal and the back part of the nasal, and contributed to sustain the palato- 

 maxillary arch ; but their most constant relations and functions are in defence and support 

 of the crura of the olfactory ganglions. 



The nasal bone (15) is single, and terminates forwards in a thick obtuse extremity. It was 

 articulated above and behind to the frontal and prefrontals, and below, by the medium of a 

 vertical cartilage, to the vomer. 



Thepetrosal (10) attains an equal size with the alisphenoid, which it resembles in form, ex- 

 cept that the notched margin is posterior. It forms the posterior lateral wall of the cranium, 

 and was articulated below with the basioccipital and basisphenoid, above with the mastoid 

 and paroccipital, behind with the exoccipital, and before with the alisphenoid : it supported 

 the cochlear division of the labyrinth containing the otolithes. 



The sclerotal consists of two subhemispheric pieces, each with two opposite emarginations : 

 the inner ones circumscribing the hole (analogous to the meatus internus of the petrosal), for 

 the entry of the nerves and vessels to the essential parts of the organ of vision, and the outer 

 or anterior emarginations supporting the cornea. The entire sclerotic, whether bony, carti- 

 laginous, or fibrous, bears the same essential relation to the vascular and nervous parts of the 

 organ of sight, which the petrous bone does to the organ of hearing, and which the turbinate 

 bones do to the organ of smell. 



The palatine bone (so) is thick and strong at its upper part, which sends off two pro- 

 cesses ; one is the essential point of suspension of the palato-maxillary arch, and articulates 

 with the prefrontal and vomer at their point of union, the other is convex and passes for- 

 wards to be articulated to a concavity in the superior maxillary. The posterior angle of the 

 base of the palatine is attached, in the Cod, by short and strong ligaments to the prefrontal. 

 The thin posterior and inner border of the bone is joined by ligament to the entoptcrygoid, 

 and its outer angle is dovetailed into the pterygoid. The palatine contributes to form the 

 floor of the orbit and the roof of the mouth, but is edentulous in the Cod. 



The maxillary (i) is here, as in most Fishes, an edentulous bone, almost wholly concealed 

 in the recent head in a fold of the skin between the palatine and premaxillary : it lies posterior 



