254 Part III. — Twentieth Annual Report 



The prfefrontals show certain differences in the three species. The 

 neck formed by the two pTa?f rentals, just in front of the frontal, is 

 comparatively narrow in the saithe, and much broader in the lythe and 

 cod. The external edge meets the posterior surface in a sharp angle in 

 the lythe, whereas in the saithe this corner is rounded ofl'. The articular 

 surface at this corner which receives the upper angle of the prseorbital is 

 much larger in the saithe than in the lythe. In the cod this articular 

 surface is very large and cut deeply into the edge of the bone. In its 

 anterior corner, too, the cod shows a prominent projecting facet for 

 articulation with the "handle" of the palatine. These expansions 

 shorten and define the neck of the praefrontals. These articular surfaces 

 in the saithe and lythe are not noticed iu the view of the skull from 

 above. 



The upper surface of the paroccipital in the cod is short and broad, 

 curved distinctly downwards and backwards : in the saithe it has a long 

 narrow surface, the bone projecting posteriorly in a long narrow angle ; 

 in the lythe the condition is intermediate between the cod and the 

 saithe. 



The paroccipitals are borne ou the ends of the lateral expansions of the 

 supraoccipital. The shape of the crescent form of the lateral expansions 

 on either side of the occipital spine is of some moment. In the lythe it 

 is a broad gentle arc ; in the saithe it is a deep bend, of irregular outline. 

 The latter condition is due to the shape of the paroccipital, which is in this 

 species bilobed to a slight degree. In the cod the crescent is very 

 shallow. The angle between the lateral expansion of the supraoccipital 

 and the occipital spine is much more acute than in the other two. The 

 posterior wall of the cranium is brought further posteriorly in the lythe 

 and cod than in the saithe. 



The squamosal in the cod ends in a broadly-rounded extremity in the 

 saithe in a sharp point, and in the lythe in an intermediate condition. 



View from Below. 

 Cod, Fig. 35, PI. VI. : Saithe, Fig. 36, PI. VI. : Lythe, Fig. 37, PI. VI. 



The vomer and the parasphenoid in the cod are much stronger and broader 

 than those of the saithe and lythe. In respect to the vomerine teeth certain 

 important differences are to be noted. In the cod the tooth-bearing area 

 is a broad chevron band. It has four to five rows of teeth, those on the 

 posterior border and at each end of the chevron being larger than the 

 others. In the saithe there is a narrow band similar in shape to that of 

 the cod, but the teeth are very minute. They are arranged generally in 

 two or three rows, and the teeth increase a little in size as they recede 

 from the apex of the bone. Sometimes the band of teeth is not 

 continuous ; in certain cases there is a break at the apex which may be 

 free from teeth. In the lythe there is not a complete chevron-shaped 

 tooth-bearing area. The teeth, which are arranged in two rows, are much 

 larger and much fewer in number than those of the saithe. The teeth in 

 the hind row are larger than those in the outer. Not infrequently there 

 is a small apical patch of teeth separated from the rows of teeth on each 

 side. 



The ventral surface of the parasphenoid in the cod is flattened ; and the 

 flat area extends forward to the end of the suture of the vomer. In the 

 saithe the flat area is very sharply defined, although not so broad as in the 

 cod ; it narrows as it approaches the end of the long suture of the vomer, 

 and in some cases is reduced to a ridge before it reaches that point. 

 There is a slight groove in the flattened area just ventral to the prootic in 



