FLAT-FISHES 89 



the turbot, Scoplitlialmus maxiimis, and the brill, S. rhombus, and 

 one to the genus J^epidorhonibus the Megrim or sail-fhike, Lei)idor- 

 hombus whifif-iagonis, hitherto known fis Pleuronectes megastoma. 

 This new terminology is rather harassing as it was a useful memoria 

 technica to associate " meg " with megrim and megastoma, the 

 latter word reminding one of the characteristic large mouth of this 

 fish. These species have tlie following characters, eyes on the left 

 side of the head, mouth large, and teeth and jaws equal on both 

 sides. 



In describing the various species of fish, the brain pattern of 

 which has been discussed, our attention has been drawn only to 

 bottom-feeding fish, and those which feed on the surface. We have 

 not, hitherto, encountered predacious fish, although the chub almost 

 deserves that description. 



It will not be unexpected, if it be found that fish with predacious 

 habits present a very different type of brain pattern. This pattern 

 is ^^■ell exemplified in the cod family as we shall have occasion to 

 describe in the following chapter, and it is also well shown in this 

 third group of flat-fishes. Before going into details, it may be 

 stated at once how different are the habits of feeding of this group 

 from those of the groups above described ; Group I feeds solely 

 on worms, and Group II feeds on worms and shell-fish, while Group 

 III has almost exclusively a fish diet. The characteristic pattern 

 of a predacious fish is the large size of the optic lobes and the somatic- 

 sensory lobes, the small size of the facial lobes and the absence of a 

 central acoustic area or lobe. 



The turbot, brill and megrim are bottom-feeding fish, and do 

 not as a rule frequent depths greater than twenty fathoms. The 

 swim-bladder is found in the post -larval stages and remains quite 

 late in this transitional stage in the turbot, and specimens have 

 been described as large as an inch long, in which it is still present. 

 The transitional stages of flounder, plaice, and dab have been ob- 

 tained near the bottom, and as they have no swim-bladder, they 

 can only swim up from the bottom by active movements of the fiins. 

 But the young turbot has a neutral buoyancy and can rise or sink 

 in the water without any active swimming. Cumiingham has 

 pointed out the advantage to the young fish of this power and habit 

 of swimming at the surface. Even at these early stages the turbot 

 and brill feed on other fishes, smaller than themselves ; and in 

 summer time the young of all kinds of fishes are more plentiful 

 on the surface than near the bottom. 



We will now describe the brain of the turbot, which may be 

 regarded as the type of Group III, and the Plate 17 will enable 



