Holt and Caldeewood — Report on the Rarer Fishes. 481 



though, as usual, there is great variation in this respect within the limits of 

 either locality. 



As regards its distribution, the long rough dab appears to be strictly a 

 Northern species. In the Old Hemisphere it ranges from Spitzbergen to the 

 English Channel, and in the New from Greenland to the New England States, 

 while CoUett suspects that it exists also throughout the Arctic Ocean. It appears 

 to attain its largest size within the more northern parts of its range ; Collett notes 

 that one of Fabricius' types, from Greenland, measures 45.1 cm., while we have 

 seen examples from Iceland which far exceeded in size any that are obtained in 

 British waters. The species was taken during the Norwegian North Atlantic 

 Expedition at a maximum depth of 223 fathoms, and it has also been found in 

 deep water on the American coast (Goode). It was not taken during the Survey 

 at any depth exceeding 80, or less than 25, fathoms. It is much commoner on the 

 eastern than on the western coasts of Great Britain, and is very abundant in 

 certain parts of the North Sea. Within the latter area it occurs, as might be 

 supposed, in comparatively shallow water, and has been taken by one of us in the 

 Humber, by the other in the estuary of the Forth, although it can by no means 

 be regarded as an estuarine form. 



Genus Hhoiubus, Cuvier. 



Rhombus megastoma, Donovan. The Sail Fluke or Megrim.* (Deep-sea.) 



Arnoglossus megastoma, . . Valliant, "Exp. Sci. Trav. et Talism. Poiss.," 



p. 188. 

 „ „ . . Holt, " Sci. Proc. Roy. Dub. Soc," vii., pp. 122, 219, 



444. 

 „ „ . . Holt, "Trans. Roy. Dub. Soc.,"N.S., v., p. 71. 



The large size of the eyes, and, as compared with the more familiar of its 

 congeners, the comparative slenderness of the skeletal sti'uctures, suggest a 

 somewhat bathybial habitat for the species before us, while, on reference to known 

 facts, it is matter of common knowledge that it is found for the most part in 

 rather deeper water than the majority of British flat fishes. So far as the west 

 coast is concerned, this view is fully supported by the experience of the Survey, 

 of which details have already been given (cf. "Sci. Proc." p. 444). We need 

 only recapitulate that by far the greater number of sail flukes taken came from 



* The usual name in Ireland and Scotland is ""Witch," hut the fish is often sold as a "White Sole," 

 probably with a view to enhancing its value, since PI. cynoglossus, the true "White Sole," is considered a 

 better fish for the table. 



TEANS. EOY. DUB. SOC, N.S. VOL. V., PAitT IX. 3 Y 



