266 Pnrt III. — Tirentietlt Annual Ileport 



Pterygoid (Pt.). 

 Cod, Fig. 37, PI. X. : Saithb, Fig. 11, PI. X. : Lythe, Fig. 11, PI. IV. 



The posterior end of the pterygoid in the cod is practically at right angles 

 to the long axis of the bone; in the saithe and lythe the hind edge is more 

 or less inclined upwards. There is a deep bend or curve in the hind part of 

 the superior edge of the bone in the cod, which is absent in the saithe and 

 lythe. In all three species the bone is broadest at its posterior end, and 

 while in the cod and lythe the superior edge turns inwards immediately 

 in front of the articulation with the metapterygoid, thereby much reducing 

 the breadth of the bone, in the saithe the upper border is carried anteriorly 

 a considerable distance before it turns inwards to any marked degree. 

 The pterygoid of the saithe has thus a broader surface and a distinctly 

 difl'erent shape from the other two species. In the lythe the bone is 

 deeply forked anteriorly, while in the cod and saithe the fork is small. 



The pterygoid is bound to the metapterygoid, and quadrate behind, 

 with the palatine in front, and superiorly with the entopterygoid. 



Palatine (PL). 

 Cod, Fig. 34, PL X. : Saithe, Fig. 9, PL X. : Lythe, Fig. 11, PL IV. 



The palatine is a trowel-shaped bone, with the handle directed anteriorly. 

 In the cod this bone is much flatter than in the saithe and lythe. In the 

 last species the long articular process which is inserted into the pterygoid 

 is a little less than one-third of the total length of the bone ; in the saithe 

 it is about one-fifth, and in the cod about one-third. 



The outer border of the blade of the trowel if continued forward would 

 in the saithe and the lythe not intersect the handle, whereas in the cod it 

 would cut the handle near its base. In the saithe and lythe the o;iter 

 border of the blade of the trowel is turned up, giving rise to a hollow 

 (saithe) or groove (lythe) on the surface of the blade. The outer corner 

 projects beyond the front edge of the blade in the lythe. The curve 

 between the under surface of the handle and the front edge of the blade is 

 in the lythe an arc of much smaller radius than that of the saithi', owing to 

 the fact that in the latter the base of the handle is thicker (dorso-ventrally) 

 than in the lythe. The corresponding arc in the cod is of even greater 

 radius than that of the saithe. 



Entopterygoi'l (en. Pt.). 

 Cod, Fig. 35. PL X. : Saithe, Fig. 10, PL X. : Lythe, Fig. 11, PL IV. 



One striking point of difierence is the small size of this bone in the 

 lythe compared with those of the cod and saithe. In the case of the first 

 the entopterygoid is a bone which shows very little character. It is 

 simply a little flat transparent bone having a toothed anterior edge and a 

 rounded slightly wavy posterior border. It is not perfectly flat ; a ridge 

 runs from its anterior superior border towards the centre of the bone. 

 Between the ridge and the outer edge there is a triangular depression. 

 The ridge and the depression are characteristic of the bones of the three 

 species. 



The entopterygoids of the saithe and cod differ mainly in the shape of 

 their posterior ends which articulate with the pterygoid. Botli have 



