584 LÖNNBERG, OBSERVATIONS ON CERTAIN FLAT-FISHES. 



The first of these however cannot by any nieans be one of the 

 parent forms of this specimen, as the difference in the size and 

 shape of mouth is so great. In the above described form the 

 mouth is rather smaller than in a normal plaice and thus it 

 cannot have originated from Drepanopsetta platessoides. This 

 comes out quite clearly from the measurements giving the re- 

 lative length of the branch of lower jaw of the blind side, which 

 is 7,4 in this form, but is about 12,0 or still more in Drepa- 

 nopsetta platessoides. But many other characteristics also show 

 plainly that there is no relationship between thera. It only re- 

 mains thus for us to make a comparison between this form and 

 Pleuronectes cynoglossus (ef. Table 4). If we, to this end, com- 

 pare the relative measurements of the pole, the above described 

 aberrant specimen and the plaice we get the following interest- 

 ing table: 



Length of head . . (percentage of total length) 



.2 hd 

 o P 



i 1 



■ i 



s 



Pleuronectes 

 platessa. 



15,0 (17) 1) 



20,2 



23,0 1) 



Greatest depth of body » > > » 



32,8 



38,8 



40,8 1) 



Least » > > > > » > 



6,3 (7) 1) 



7,8 



7,9 1) 



Postorbital length of head » > ^ > 



8,4 



14,0 



15,5 1) 



Length of branch of lower jaw on the blind side 

 (percentage of total length) 



5,2 



7,4 



8,2 1) 



Distance between the anal fin and tip of snout 

 (percentage of total length) 



21,5 (24) 1) 



28,9 



30,6 1) 



Length of the pectoral fin of the eye side 



(percentage of total length) 



9,4 



8,6 



10,1 n 



» » > ventral fin of the eye side 



(percentage of total leugth) 



(i,(i 



8,0 



8,1 1) 



> > > middle rays of the caudal fin 



(percentage of total length) 



17,ti 



18,1 



18,6 M 



Nuniber of rays of the dorsal fin 



100(— 112) ') 



74 



63—76 1) 



> > > > anal ^ 



85(-100) 1) 



56 



52—57 1) 



As is apparent, most of these measurements are to a greater 

 or less extent intermediate, some being more closely related to 



*) According to Smitt. 



