252 Part III. — Tiventieth Annual Report 



The terminology which I have followed is with one or two exceptions 

 that adopted by Giinther* and Boulenger.f 



The descriptions are made on the bones of the left side of the fish. 



Skull. 



Vieio from Above. 



Cod, Fig. 31, PI. V. : Saithe, Fig. 33, PI. V. : Lythe, Fig. 34, PI. V 



In the case of fishes of equal length the skull of the cod is larger and 

 more massive than that of the saithe, while that of the latter is greater 

 than the skull of the lythe. Seen from above, the skulls much resemble 

 one another. One point of considerable importance separates the skull 

 of the cod from the other two, and that is that while in the former the 

 front edge of the ethmoid is exactly above the anterior edge of the 

 vomer, in the saithe and the lythe the ethmoid is situated well behind the 

 front edge of the vomer ; so that in the view from above nearly all the 

 upper surface of the expanded portion of the vomer is seen. * 



Another point of dilTerence is in the shape of the frontal. In the 

 lythe the anterior end of the frontal is almost square across, in the cod 

 and saithe it is more tapered and pointed. The ethmoid in the cod has a 

 superior surface of considerable length and breadth ; but in the saithe it 

 is reduced to a short, sharp ridge. In the lythe it is broader than in the 

 saithe. The hind portion of the ethmoid which articulates with the 

 frontal is continued backwards in the latter bone as a distinct broad 

 ridge, extending back to the foramina. In the saithe such a ridge is to 

 be traced, but in this fish it is not prominent, while in the lythe it is 

 absent. 



The two large foramina in the frontal show certain differences. In the 

 cod and saithe they usually end anteriorly in a narrow angle, though 

 sometimes both ends are rounded. In the lythe they are kidney-shaped, 

 and are on the whole wider than those of the cod and saithe : anteriorly 

 they are turned outwards and have their margins rounded. The posterior 

 end is distinctly wider than the anterior. Not infrequently the shape of 

 the foramen is altered by little bony processes which arise from the 

 margins. In the lythe and saithe the foramina are deep, their hind 

 margins being high. In the cod they are shallow. 



The lamellae which form the grooves which lodge the sapraorbital 

 canals differ in the three species. In the cod the lamella is broader than 

 in the other two ; and in the lythe it is distinctly higher than in the 

 other two. The lamellae of the two sides gradually approach each other 

 as they proceed anteriorly, until they reach the anterior ends of the 

 foramina in the cod, and from this point they turn outwards very 

 slightly, and then bend inwards, being separated at the front end of the 

 frontal by about the same distance as at the level of the foramina. In the 

 saithe the lamellae approach one another a little more closely at the 

 foramina than they do in the cod. In that region the groove formed by 

 the overhanging lamella is converted into a closed bony canal by the 

 presence of a vertical plate connecting the outer edge of the lamella with 

 the main part of the frontal. In the lythe the lamellae, after approaching 

 close to one another about the middle of the foramina, bend sharply 

 outwards, and then inwards toward the median line. The vertical wall 

 of the closed canal, however, is continued outwards to the anterior outer 

 corner of the frontal, making a very wide funnel-like mouth to the canal. 



* Gunther. The Study of Fishes. Edinburgh, 1880. 

 t Boulenger. Catalogue of the Percif orm Fishes in the British Museum, 2nd edition. 

 London, 1895. 



