of the Fishery Board fur Scutland. 281 



Postclavicle (pt. CI.). 

 Cod, Fig. 12, PI. XL : Saithe, Fig. 4, PI. XI. : Lythe, Fig. 24, PI. IV. 



The postclavicle is subject to a large amount of variation ; this is 

 especially the case in the cod. 



This bone has a long shaft vvith an expanded head. In the lythe and 

 saithe it is a slender thin bone, in the cod the stalk is thick and 

 irregular. 



The expanded head of the bone in the lythe is short and trumpet- 

 shaped ; that of the saithe is usually a long parallelogram-shaped piece, 

 showing sometimes, however, a broadened extremity, which gives it a 

 trumpet form. The head is set at an angle to the stalk. In the cod the 

 head of the bone is helmet-shaped ; its extremity is rounded, not straight 

 as in the saithe and lythe, and it has on its posterior side a small beak- 

 like process. 



The trumpet shape can be traced more or less distinctly in the heads of 

 these bones in all the three species, though in the saithe and cod it has 

 been concealed by a bony development in the angle between the head 

 and the stalk. In the cod the trumpet-shaped area is short, and very 

 wide at its base. 



Tn one cod — a male measuring 94 cm. — a remarkable condition was 

 found. The trumpet-shaped area had developed greatly in a backward 

 direction, not, as is usual in the cod, in an upward direction ; it therefore 

 projected well in advance of the portion filling up the angle between the 

 head and the stalk. The head had thus a broad sickle shape. 



In the usual form of the postclavicle of the cod the little posterior beak 

 is the corner of the original trumpet-shaped area. The head of this bone 

 is two-layered — the outer is the trumpet-shaped part, and the inner is the 

 layer which has filled up the angle between the head and the stalk and 

 which has extended up under almost the whole of the funnel-shaped area. 

 The two layers are seen distinctly in the region of the beak. 



The double-layered condition of the head is not present in the saithe 

 and lythe. 



The postclavicle is attached by ligaments to the upper border of the 

 clavicle. 



Pelvic Arch. 



Innominates (Inn.). 



Con, Fig. 8, PI. XL : Saithe, Fig. 1, PI. XL : Lythe, Fig. 17, PI. IV. 



The innominates articulate anteriorly with one another and posteriorly 

 with a ligament which lies between them. The ventral surface of the 

 bone is concave. Each innominate bone has three articular surfaces — viz., 

 two hollow articular processes, anterior and posterior, and a broad curved 

 hind edge which articulates with the ventral fin-rays. 



The innominates of the cod are very much larger than those of the 

 saithe, while those of the saithe greatly exceed those of the lythe. In 

 general appearance those of the saithe and cod resemble one another, 

 and differ much from those of the lythe. 



Between the anterior and posterior narrow articular processes there is 

 in the cod and saithe a sheet of thin transparent bone. A cavity of more 

 or less definite shape is cut out of this sheet of bone. Thus, if the united 

 innominates are examined it is seen that in the saithe the cavities of either 



