of the Fishery Board for Scotland. 253 



In the cod and saithe the mouth of the canal is small in comparison to 

 that in the lythe. The space in front of the foramina and between the 

 edges of the lamellii? is in the cod fairly flat, though it shows a distinct 

 median ridge, the continuation of the process from the ethmoid, and on 

 either side of that a shallow longitudinal groove. In the saithe and 

 lythe, however, there is a broad, deep depression between the prominent 

 edges of the lamell?e. In the hind portion of the frontal the lamella is 

 seen to be two-layered. This is apparent only at its posterior end, 

 where the lower layer appears projecting from below the upper. The 

 posterior edge of the upper layer is irregular, but may be traced to a 

 connection with the beginning of the ridge in the parietal. In the cod 

 this may be made out in only a few skulls, but the two layers are very 

 distinct in the saithe and lythe. In the lythe there is a larger portion of 

 the lower layer free from the upper layer than in the saithe. 



The outer edges of the frontals in the cod and saithe are only slightly 

 curved inwards over the orbit : in the latter more so than in the former ; 

 but in the lythe there is a deep incurving in that region. 



The occipital spine is a continuation of a prominent ridge or spine on 

 the frontal. In very few specimens is the anterior portion or origin of 

 the frontal spine perfectly median : it is usually deflected to one side or 

 the other. In the cod this spine ends anteriorly at some distance behind 

 the two large foramina. In the saithe it begins at the hind border of the 

 foramina, and is to be traced still further forward as a ridge between the 

 two cavities. In the lythe, in which the septum between the two 

 foramina is much broader than in the saithe, the forward continuation of 

 the spine is not always well marked, but may usually be traced. In the 

 cod, however, in front of the origin of the spine, and between it and the 

 hind borders of the foramina, there is a depression which sharply defines 

 the front extremity of the spine. 



On the posterior portion of the frontal there is on either side of the 

 frontal spine a ridge running from the angle between the spine and the 

 lamella, backwards and outwards. It practically bisects this angle, and 

 is continued directly into the ridge on the parietal, which further back 

 rises into the crest of that bone. In the saithe and lythe this ridge is 

 very well marked : in the cod it is with difficulty made out, since the 

 ridge on the parietal is reduced to a mere line. The frontal and parietal 

 are dovetailed into one another. In the saithe a broad, and usually long, 

 dovetail of the parietal is inserted in the posterior border of the frontal, 

 between the spine and the oblique ridge, while a process, which is a 

 continuation of the ridge on the frontal, runs backward and well up the 

 ridge on the parietal. The same condition exists in the lythe, but 

 generally the ridge process is much shorter than in the saithe. The same 

 general arrangement of interlocking may be followed in the case of the 

 cod. In two saithe skulls (male) the frontal ridge processes rose at their 

 extremities into crests, which projected above the level of the adjacent 

 parietal ridge. In the posterior external corner of the frontal there is a 

 notch, in which lies the superior suborbital. This notch is deeper in the 

 cod and lythe than in the saithe. The anterior margin of the notch 

 meets the adjacent part of the edge of the frontal in a sharp corner in the 

 lythe : in the saithe it is broadly rounded. In the cod the front margin 

 of the notch projects backwards over it. 



The crests of the parietals in the saithe and lythe are very large. They 

 are directed upwards and outwards. In the cod they are small flat 

 triangular processes covering the foramen for the exit of the nervus 

 lateralis. In the saithe and lythe the under surface of the crest is pierced 

 by this foramen. 



