THE FLAT-FISH FAMILY 209 



occasionally taken in which the dorsal fin does not extend for- 

 ward in the usual manner, but forms a hook overhanging the 

 eye nearest it, and in these specimens it is easier to see how the 

 face is twisted. 



There are no large spines in the flat-fishes in the fins or on 

 the bones of the head, but a small one projects in some in front 

 of the ventral fin. The scales are variously developed ; in some 

 they are present all over the body and have a spiny margin as 

 in the common dab, in others they are rudimentary as in the 

 plaice, in others they are developed into rough tubercles as in 

 the flounder and turbot. It should be noted that in these fishes 

 the great extension of the ventral fin causes the vent to have a 

 - position very near the head ; it is further forward than even in 

 the whiting and other fishes of the cod family. The opening of 

 the roes is just behind the vent, also in front of the ventral fin, 

 but the belly cavity being very small the greater part of the roe 

 on each side is situated behind it, between the flesh and the par- 

 tition of bony spines in the middle of the body. 



The following are the British species with their distinctions: 



I. Species with the eyes on the right side, the mouth at the 

 end of the snout, teeth most developed on the blind side. 



1. The Plaice. Scales small and embedded in the skin ; 



bony knobs on the head behind the eyes, red spots on the 

 upper side. 



2. The Flounder. Rough tubercles along the bases of the 



marginal fins, and along the lateral line. 



3. The Dab. Scales all alike, with toothed edges, making 



the skin rough. 



4. The Witch. Shape oblong, scales all alike, very slightly 



toothed on upper side : blister-like cavities beneath the 

 skin of the head on the lower side. 



5. The Lemon Dab. Scales small and smooth, skin very 



slimy, head and mouth very small, colour yellowish brown 

 mottled with large round marks. 



II. Species with eyes on the right side, mouth large and jaws 

 similar on the two sides. 



6. The Halibut. Scales smooth, lateral line with a curve, 



size very large. 



P 



