198 FLOUNDER. 



from the origin of the dorsal fin forward, and this has been 

 accompanied with a black surface below; but it seems probable 

 that this greater frequency of variation is only because the 

 fish itself is more frequently caught than other species of the 

 family of flatfishes. The yellowish spots which sometimes mark 

 its sides are very different from those which adorn the surface 

 of the Plaice. 



But as regards the variety (here figured) which is marked 

 with a notch or deficiency in the outline behind the eyes, 

 and a black surface on the under side, it has occurred so 

 frequently in some districts as to have raised the suspicion of 

 its being truly a distinct species, the more especially as some 

 difference in the fins has also been detected. But after 

 comparing an example from the River Fowey with a specimen 

 of Flounder of regular formation, I feel no doubt of their 

 being specifically the same; while, on the other hand, I feel 

 equally certain that this variety of structure in the outline is 

 natural, and not, as has been supposed, the consequence of 

 mutilation. 



Some observations which have been made on the structure 

 of the mouth and cheeks of this fish are probably applicable, 

 with a little variation, to the other flatfishes already described; 

 for the want of symmetry, which is the character of this 

 family, extends to all the tissues or portions of the head, 

 including the nerves of feeling as well as the muscles and 

 bones, and thus creating in the upper surface a far higher 

 degree of power and sensibility than exists in the lower. Thus, 

 what appears to be the largest nerve in the body is seen to 

 pass along the coloured side of the cheeks, to be distributed 

 to the palate, in comparison with which there does not appear 

 to be any one on the lower side, while there is another here 

 situated which passes down to supply the angle of the jaw. 

 On the coloured side the (masseter) muscle of the jaw is 

 strong, and is united to that bone by a tendon, which is not 

 the case on the white side; and a separate nerve, somewhat 

 corresponding to that already mentioned on the white side, is 

 given out from the skull proportionally further forward, from 

 whence it descends under the tendon to the jaw, both these 

 nerves being accompanied with blood-vessels. 



