of the Fishery Board for Scotland. 



227 



Nine specimens of the long rough dab are figured, ranged into an 

 elongated and a shorter series, as it was found impossible to arrange the 

 specimens into a single regular series. They extend from 9 •37mm. to 

 14-77mm. The two larger specimens, 13-87mm. and 14-77mm., are 

 shown to be remarkably like dabs, the proportions being similar. So far 

 as the drawings show, also, the mouth is very slightly different from that 

 of the dab. The asymmetry of the head is more advanced in the common 

 dab, and also the pigmentation. Myomeral streaks are present in the 

 long rough but absent in the common dab. The number of fin-rays in 

 the long rough dab is greater than in the common dab, though at these 

 early stages the difference is not great. 



The smaller specimens are divided into two series — in the one the eye 

 has not begun to migrate, in the other it has just commenced; but the 

 difference is extremely slight : another difference of more importance 

 being the greater breadth of those which are further advanced. In the 

 absence of later specimens over 15mm. there was great difficulty in seeing 

 the relations between these smaller series and the larger specimens of 

 13 •87mm. and 14*7 7mm. Mr. Holt makes a reference also to the 

 specimens mentioned in the " Researches " as long rough dabs. While 

 working up his material at St. Andrews he had evidently seen these 

 specimens, and noted that they exhibited "a depression between the 

 eyes " and a " preponderance of pigment along the ventral line." 



Later specimens, from 27mm. onwards, were also obtained by him. 

 There was no doubt that these were long rough dabs, the characteristics 

 being sufficiently obvious even in the smallest at 27mm. All these 

 specimens were taken in very deep water, the smaller, metamorphosing 

 examples, being obtained from 30 to 32 fathoms, the larger, with adult 

 characteristics, from 40 to 80 fathoms. 



The difficulties Mr. Holt had to encounter arose from the lack of 

 complete series. He was thus compelled to trust to differences in 

 measurements —proportions of breadth to length, head to length, &c. ; but 

 where variations are considerable, measurements are not altogether 

 trustworthy, unless one knows the limits of variation. Indeed, Mr. 

 Holt was quite nonplussed with the amount of variation in the long 

 rough dab. 



Mr. Cunningham, in "Marketable Marine Fishes" (1896), criticises 

 Holt's work. He is of the opinion that the long rough dabs of Holt are, 

 the longer specimens plaice, the smaller dabs. He seems to think, too, 

 that the metamorphosis of the dab is completed at an earlier stage than 

 that of the plaice, for he says (p. 225) : — " Considering that when first 

 hatched tlie larva of the dab is little more than half the length of that of 

 the plaice, it is singular that it should be longer than the plaice during 

 the process of transformation." 



On p. 218 he gives a drawing of the "Larva of Plaice," a little over 

 15mm. long, with its eye on the ridge. Comparing this drawing with 

 those by Holt, it evidently corresponds either with the dab or the long 

 rough dab. Mr. Holt's specimens were in spirit, Mr. Cunningham's 

 alive. With regard to the long rough dab, Mr. Cunningham thinks that the 

 young forms have not yet been identified. 



Dr. Ehrenbaum,* more recently, has described and figured the young 

 larval forms of these species. A number of the young post-larval stages of 

 the plaice were obtained by trawl-net, and the characteristics of this 

 species, from the larval stage to the assumption of the adult characteristics, 

 are placed in tabular form. He describes also the early post-larval 

 stages of the flounder. The post-larval stages of the dab were not 

 obtained, however, nor those of the long rough dab and lemon dab. 

 * Ever u. Larven von Fischen der Deutschen Bucht. Wissen, Meere, 1896. 



