THE PLAISU. 301 



Firth of Forth in the neighbourhood of Alloa. It feeds 

 on small insects, and sheds its spawn in April. 



Family VI. PLEURONECTID^.— Body flat, com- 

 pressed vertically ; back of a dark colour ; under surface of 

 a pure white ; dorsal fin single, extending the whole length 

 of the back ; both eyes placed on the same side of the head. 

 The species' keep close to the bottom, having no swimming 

 bladder. 



Genus PLA TESSA. Both eyes on the right side; dor- 

 sal fin commencing over the left eye, and not reaching to 

 the caudal ; caudal fin rounded at the end. 



Platessa vulgaris.* — The Plaise. 



Specific Characters. — A row of five or six osseous tubercles on the 

 eye side of the head ; scales entire. (See Plate XXXVII.) 



Description. — From a small specimen a foot in length. Head ra- 

 ther less than one-fourth of the entire length, caudal included; breadth 

 of the body half its length, fins not included. Colour of the body 

 above brownish, with large distant orange spots ; under surface pure 

 white, occasionally mottled. Dorsal fin commencing over the mid- 

 dle of the orbit, and terminating at a short interval from the base of 

 the caudal; the middle rays the longest, more than twice the length 

 of the first. Anal fin arising under the middle of the pectoral, and 

 ending under the last ray of the dorsal ; the sixteenth, seventeenth, 

 and eighteenth rays the longest, more than twice the length of the 

 first, the succeeding ones gradually diminishing ; the last very short ; 

 caudal even or slightly rounded at the end ; the middle ray as long 

 as the base of the fifteen first dorsal rays ; ventrals as long as the 

 fifth or sixth ray of the anal, and situated in advance of the base of 

 the pectorals; a strong spine placed in front of the anal; pectorals 

 rather longer than the ventrals ; snout pointed ; body contracted at 

 the base of the tail; under jaw longest, ascending; mouth small ; 

 teeth even, closely set and rather obtuse ; eyes on the right side, full 

 and prominent, both equally advanced towards the end of the snout ; 



* Platessa vulgaris, Yarr., Jen., Flem. Plcuronectes platessa, Linn., 

 Penn., Bloch. Fluke. 



