472 BULLETIN OF THE BUEEAU OF FISHEEIES 



General range and occurrence in the Gulf of Maine. — This is a deep-water ground 

 fish which has been taken at many locaUties off the American coast from the West 

 Indies and Gulf of Mexico northward along the continental slope to abreast of 

 southern New England in depths of 104 to 464 fathoms. It is included here because 

 once recorded off Nantucket in 148 fathoms, but this is apparently about its eastern 

 limit for it has not been reported from the slope of Georges Bank and hence is 

 hardly to be expected in the Gulf of Maine proper. 



THE FLOUNDERS AND SOLES. FAMILIES PLEURONECTID.ffi AND SOLEID.E 



The flatfishes are a very homogenous tribe, so different from all other fishes 

 that no one is apt to take one for any other fish. What strikes one first is their 

 flatness; less obvious is the fact that they lie not on the belly but on one side, right 

 or left; and the skull so twists in the course of development that the eye, which was 

 originally on the side fated to be underneath, migrates around the head so that 

 both eyes finally come to lie close together on the side that is uppermost as the 

 fish lies. The mouth, however, more nearly retains its original position and hence is 

 often described as opening sidewise. The larval flounder swims on edge like any 

 other fish, the migration of the eye taking place just before the fry take to the 

 bottom. 



All flounders have a single long fin on each edge, one the dorsal and the other 

 the anal, with well-developed ventrals. Most of the Gulf of Maine species also 

 have large pectorals, one on the upper side as the fish lies on the bottom and the 

 other on the lower side. The ventrals are in front of or in fine with the pectorals, 

 the abdominal cavity is very short, and some species are armed with a stout anal 

 spine. The distinction between the two families is indefinite and bridged by several 

 genera which are more or less intermediate between them. Most Gulf of Maine 

 flatfish are typical flounders (Pleuronectidag) , the soles (Soleidse) being represented 

 there by the hog-choker (p. 522) alone. 



Our several flatfishes look much alike. Indeed, they are often confused, but 

 it is not difficult to tell one from another as the diagnostic characters are rather 

 precise, if not obvious at first glance. Huntsman (1918c) has published a very 

 useful key to the eastern Canadian species, which is expanded here to cover the 

 Gulf of Maine. 



KEY TO GULF OF MAINE FLATFISHES 



1 . Eyes on the left side (guts at left edge as the fish lies) 2 



Eyes on the right side (guts at the right) 5 



2. Lateral line arched over the pectoral fin" 3 



Lateral line straight Citharichthys arctifrons, p. 521 



3. The two ventral fins are alike 4 



The two ventrals are not alike, the left (upper) being continuous with the anal fin, the 



right (lower) separate from it Sand flounder, p. 516 



4. Upper side with four large oblong black eye spots; less than 75 rays in the long (dorsal) 



fin Four-spotted flounder, p. 494 



Upper side with many small spots; more than 85 dorsal fin rays.. Summer flounder, p. 491 



5. There is a well-developed pectoral fin on the eyed side • 6 



No pectoral fins Hog-choker, p. 522 



" In all the flounders of this type so far recorded from the Gulf of Maine both pectorals are well developed. Should one be 

 taken with no pectoral fin on the blind side it would probably be the deep-water Monolene seasiUcauda (p. 521). 



