of the Fishery Buardfor !::>cotland. 279 



corner of the coracoid is white and well ossified. There is in all three a 

 more or less well marked strengthening rib running from the hilum of the 

 bone down to the point on its posterior edge wliere the tendon unites the 

 free end of the coracoid to the clavicle. This ridge is especially thick 

 in the cod, and between it and the anterior edge there is a gusset-shaped 

 area of thin transparent bone, similar to the general structure of the 

 clavicle in the saithe and lythe. En the cod, on the front side of the 

 thickened bracing ridge there is a thumb-like depression on the bone. 

 The strengthening ridge is comparatively insignificant, so far as thickness 

 is concerned, in the saithe and lythe, but it is readily noticed from the fact 

 that its striae run across the general growth layers of the bone. 



The bones differ in shape. The posterior edge of the lower half is 

 more rounded in the saithe than in the lythe and cod. The bone is 

 wider in its lower half in the former than in the two latter. 



The anterior edge of the clavicle is curved, showing in side view a 

 concave outline. The deepest part of the curve is in front of the scapular 

 region. This hollow is in the saithe filled up with a broad ledge, which is 

 absent or very small in the lythe and cod. In the saithe this ledge 

 passes inferiorly on to the internal edge of the clavicle, leaving a distinct 

 hollow between the prominent outer edge and itself. In cases where an 

 apparent lodge is present in the cod and lythe the last condition does not 

 obtain. In the saithe the hind border below the articulation with the 

 scapula is straight for a little bit, and is parallel to the above ledge. In 

 the cod the hind edge is here rounded, while in the lythe the anterior 

 and hind edges are more or less parallel. 



The hind superior process of the clavicle is in the cod short and narrow, 

 whereas it is in the saithe broad, especially at its base. In the latter it 

 makes, with the upper part of the hind edge of the bone, a less angle than 

 in the cod and lythe. In the lythe the process is short and broad. 



The superior vertical process of the clavicle, upon which articulates the 

 supraclavicle, is prominent in all three species. In the saithe the angle 

 between it and the superior edge of the bone is nearly a right angle : in 

 the cod and lythe it is very much greater than a right angle. In the cod 

 and lythe the superior process is usually pointed : in the saithe it is 

 commonly truncated. 



In the cod and saithe there is in the hind edge a distinct corner at the 

 point where the coracoid ligament is attached : in the saithe the posterior 

 border is evenly curved and does not exhibit this angle distinctly 



On the internal surface of the clavicle there is the raised plate to which 

 is articulated the scapula. The inferior and posterior edge of the plate is 

 in the cod smooth except at its upper corner, where it is split into 

 articular leaf-like processes. In the saithe the hind border is similar to 

 that in the cod except that it has near its lower corner a few very small 

 articular teeth. In the lythe, on the other hand, there are at the second 

 articular part fairly large projecting articular laminpe. 



There is a high ridge on the internal surface of the lower half of the 

 bone. In the saithe it is a broad thin plate : in the lythe it is consider- 

 ably narrower and thicker, while in the cod it is very thick and similar 

 in height to that of the lythe. 



Scapula (Sc). 



Cod, Fig. 13, PI. XL : Saithe, Fig. 6, PI. XI. : Lythe, Fig. 30, PI. IV. 



The scapula articulates with the clavicle by means of a sutured portion 

 above, and it is bound by a ligament in front to the hind surface of the 



