PECULIARITIES OF PLAICE FROM DIFFERENT FISHING GROUNDS. 343 



more closely allied to the plaice and flounder, and also has ctenoid 

 scales all over its body, except the area covered by tlie pectoral fin ; 

 ctenoid scales extend also on to the fin-rays. Now it is not a fact that 

 the dab inhabits more northern regions tlian the plaice, and still less 

 than glacialis. On the contrary the dab and plaice are constantly taken 

 together on the same ground. The dab extends on the European coast 

 from the Bay of Biscay to the Kara Sea, and is plentiful on the south 

 coast of Iceland, and is found in the Baltic at least as far east as Goth- 

 land. On the American side of the Atlantic the dab lives in the same 

 latitudes as glacialis, but in a sliglitly different form, described by 

 American naturalists as a distinct species, under the name Limanda 

 ferruginea. In the North Pacific, however, we do find that the local 

 form of the dab, like the local form of the flounder, is rougher than 

 in other parts of the world. This form is described under the name 

 Limanda aspcra, and extends from Sitka and Saghalien to Wrangel 

 Island off the coast of Siberia. Thus, although we find here again that 

 rougher scales in the same species characterise the more northern forms, 

 and appear to indicate a direct influence of climate, we do not find 

 that northern and southern species are constantly distinguished by a 

 similar difference in the character of the scales. The occurrence of 

 spinulation as a secondary sexual character, developing in the males, as 

 such characters generally do, only when maturity is reached, is peculiar 

 to the plaice, and at present we have no evidence that, as Duncker 

 suggests, the character is of any importance in the relations of the 

 sexes. 



