of the Fishery Board for Scotland. 263 



head of the bone is higher in the saithe than in the lythe ; iu the latter 

 it 16 more rounded on its anterior edge. In side view there is in the 

 anterior end of the bone a cleft between the base of this plate and the 

 beginning of the toothed area. The prominence of this cleft, which is 

 deeper in the lytlic than in the saithe, is worthy of notice. In the latter 

 there is a considerable thickness of bone, rounded in front, between the 

 base of the plate and the lower surface of the premaxilla ; in the lythe 

 the breadth of the cleft reduces this to a very thin strip. 



The smaller process on the head of the premaxilla articulates with the 

 lower part of the head of the maxilla. The higher process of the pre- 

 maxilla of one side is bound by a long ligament to the base of the process 

 of the palatine on the other side. Behind the two premaxillae there is a 

 large cubical mass of cartilage which serves to connect them with the 

 front of the ethmoid. 



Maxilla (M.). 



Cod, Fig. 10, PL X. : Saithe, Fig. 13, PI. X. : Lythe, Fig. 2, PL IV. 



The maxilla of the cod is a longer bone than that of the saithe and 

 lythe, and in the two latter the head of the bone is bent downwards 

 more than in the former. At the anterior part of the head of the maxilla 

 there is a facet for articulation with the premaxilla. In front of it there 

 is a prominent projecting edge which in the saithe and lythe is semi- 

 circular in shape, and in the cod roughly triangular. Alongside the 

 articular facet just mentioned there is a large tuberosity iu the cod, which 

 is absent in the saithe and lythe, or marked in the latter by a slight 

 elevation. A ligament binding the maxilla to the premaxilla is attached 

 at this point. 



The maxilla articulates with the premaxilla iu front, behind with the 

 vomer, and above with the process of the palatine. Its free end is 

 united by means of cartilage to the end of the premaxilla, and also by a 

 thick round cartilaginous ligament to the depression on the outer surface 

 of the dentary. 



Articular (Ar.) and Annular (Au.). 

 Cod, Fig. 43, PL X. : Saithe, Fig. 19, PL X. : Lythe, Fig. 13, PL IV. 



A first point of difference is seen in the shape of the potterior end of 

 the articular. Its hind region has a broad ventral expansion which is 

 larger in the saithe and lythe than in the cod. In articulars of the same 

 size the angular of the cod is much larger thau that of the other two 

 species. The angle between the lower plate and the rest of the articular 

 is nearly a right angle ; in the saithe and lythe it is much less. The 

 three forms differ from each other in respect to the share which the 

 angular takes in the lower edge of the ventral expansion. In the lythe 

 the angular forms less than one-half of the lower margin, in the saithe it 

 constitutes a little more than one-half, aud in the cod three-fourths of 

 the same. The sharp extremity of the plate is carried farther forward in 

 the lythe than in the saithe. On the long shield of the Meckel's cartilage 

 there is a high longitudinal ridge ; in the saithe and lythe it is rounded 

 off. 



The posterior border or rim of the cavity which serves for articulation 

 with the quadrate projects in a triangular mass, to which is attached the 

 ligament binding the articular and quadrate together. In the cod thia 



