FLAT-FISHES 77 



Tho follo^^•i^<:J table shows the position of the fishes according 

 to tlie latest classitication : 



Family Sub-family Species 



1. Pleuronectidoi . Pleuronectince . Hippoglosstis. Halibut. 



Pleuronectes limanda. Dab. 

 ,, Platessa. Plaice. 

 „ Microcephalus. 



Lemon sole. 

 ,, Cynoglossus. Witch. 

 ,, Flesus. Flounder. 



2. Bothidce . . ScophtJialmincc . Rhombus maximus. Tui-bot. 



,, laevis. Brill. 



Lepidorhombus ivhijf- 



iagonis. Megrim. 



3. Soleidce . . Solea solea. Sole. 



We now propose to study the brain pattern of the Heterosomata 

 and we shall find that the members of this family fall into groups, 

 which, it is interesting to note, closely correspond with the four main 

 groups of British flat-fish, as described by Cunningham. We shall 

 take these groups in the following order : 



Group I. — Species with eyes on the right side. Teeth only on 

 the blind side. A " beard " on the lower side of head. Example, 

 the sole, Solea vulgaris. 



Group II. — Species with the eyes on the right side. Teeth most 

 developed on blind side. Examples, the plaice, the lemon sole, 

 the witch, the dab and the flounder. 



Group III. — Species with eyes on the right side. Mouth large. 

 Jaws similar on two sides. Example, the halibut. 



Group IV. — Species with the eyes on the left side. Teeth and 

 jaws equal on both sides. Examples, the tiurbot, briU and megrim. 



The examples mentioned are those fish which we have had the 

 opportunity of examining both in the fresh state and by the study 

 of serial sections. The asymmetry of the head, the upward aspect 

 of the eyes and the crossing of the optic nerves have been fully 

 discussed by many authorities : but, as for practical purposes, those 

 parts of the brain, which concern us, are nearly symmetrical, we do 

 not propose to make any further reference to these characteristic 

 features. 



