278 Part III. — Twentieth Annual Report 



over this interval which makes the tyfo grooves continuous, but without 

 hiding the interval completely. In the lythe and saithe the fold covering 

 the anterior groove is much narrower than the same in the cod, in which 

 it reaches in the greater part of its length down close to the inferior edge 

 of the bone. The grooves lodge the infraorbital sensory canal. The 

 anterior fold is rather wider in the lythe than in the saithe. The 

 articular surface for attachment to the prefrontal is much broader in the 

 saithe and cod than in the lythe. 



Suborbitals (sb. Or.). 



Cod, Fig. 28, PI. X. : Saithe, Fig. 3, PI. X. : Lythe, Figs. 5, 6, 8, 9, 10, 



PI. IV. 



There are certain differences between the five suborbitals of the three 

 species, but they are minute. 



The second suborbital is in the saithe semicircular in outline ; in the 

 lythe it is nearly twice as long as it is broad, while in the cod it is longer 

 than it is broad, but not so long ])roportionally as in the lythe. 



The third suborbital is in the cod wider at its inferior end, and the 

 lower anterior corner projects. 



The fifth suborbital in the saithe and lythe is short ; its superior 

 extremity is much thicker than the inferior. In the cod it is a lighter 

 though longer bone than in the other two. The top end is rather wider 

 than the lower. The bone is excised more or less all over in a sort of 

 fretwork fashion. 



Supratemporals (s. T.). 

 Cod, Fig. 29, PI. X. : Saithe, Fig. 8, PI. X. : Lythe, Fig. 22, PI. IV. 



The supratemjDorals are four in number. The most remarkable in form 

 is the second, which is a sort of unclosed tube. It is formed by the 

 infolding of either edge to meet (but not to unite) in the middle line. The 

 anterior inturned fold is shorter than the other, and moreover the fold 

 is broader superiorly than it is inferiorly. In the saithe the inturned 

 edges come close to one another, sometimes overlapping slightly. In the 

 lythe there is usually a considerable space between the two edges. 



In the saithe and lythe the ossicles resemble one another very much 

 and differ markedly from that of the cod. In the latter the edges of the 

 inturned folds are bent upwards. The second supratemporal is a flatter 

 bone in the saithe and lythe than in the cod. 



The third ossicle is bevelled at both ends. 



The fourth supratemporal is a scoop-shaped bone having its anterior 

 end more or less bevelled to fit the lower portion of the second ossicle. 

 In the cod its posterior end is deeply notched ; in the saithe and lythe it 

 is bevelled, or slightly notched. 



Pectoral Akcu. 



Clavicle (CI.). 



Cod, Fig. 10, PI. XI. : Saithe, Fig. 2, PI. XI. : Lythe, Fig. 3, PI. IV. 



The clavicle of the cod is readily distinguished^from those of the saithe 

 and lythe. In the two latter the hind edge of the bone is thiu and the 

 margin is of transparent bone, whereas in the cod the posterior edge is 

 thick and the whole of the bone superior to the level of the inferior 



