42 



much less so. In former times plaices mauy more and much 

 larger seem to have been taken in the Zuiderzee , than at 

 present is the case. The largest plaices which now are met 

 with in that sea are one foot long at best (the fish is measured 

 here , as in all other cases , from the tip of the head to the 

 end of the tail-fin). A few specimens of that size were taken in my 

 presence near the east margin of the Eukhuizer Zand. Most curious 

 1 think is the fact that so very many very small plaices are 

 taken — and sacrificed — in the Zuiderzee. They are all con- 

 sidered as young flounders and I must confess that it is not so 

 very easy to distinguish them from one another at first sight. On 

 beginning my investigation in March and April 1888 I did not 

 find so very many of these small flatfishes in the „kuil" nets; after- 

 wards the number iucreased and then I was struck by the cir- 

 cumstance that so many of the so-called small flounders were 

 small plaices. I collected some of them every time and after- 

 wards settled by accurate investigation that the smallest of the 

 little flatfishes collected and by far the greater part of them 

 were young plaices , and not young flounders Larger specimens 

 of these two fishes are easily distinguished from one another 

 only by touching them: the plaice is smooth at the lateral line 

 and also along the insertion of the unpaired (dorsal and anal) 

 fins , whereas the flounder is rough , armed with spines at those 

 places. When the fishes are very small one can hardly rely upon 

 that characteristic , as the flounders in that condition show this 

 roughness to a very small degree only. To distinguish the fishes 

 from one another in that case one is obliged to recur to coun- 

 ting the number of the rays of the dorsal and anal fins — 

 this done, the danger of erring is quite eliminated. The plaice 

 has 65 to 77 rays in the dorsal and 50 — 57 rays in the 

 anal fin ; the flounder 58 to 64 rays in its dorsal and 40 — 45 

 rays in the anal fin. I investigated 54 smaller flatfishes taken 

 with the kuilnets; 24 of these were under 70 millim. long, 20 

 measured from 70 to 100 raillim., whereas the others were longer 

 than 100 millim. 33 of these were young plaices and 21 flounders 



