436 



SCANDINAVIAN FISHES. 



The nostrils are set on the eve side in the niesial line 

 of the nasal region in front of the eyes, the posterior 

 nostril in a line with the anterior margin of the eyes, 

 the anterior about the diameter of the pupil further for- 

 Avard. On the blind side they are set somewhat higher, 

 but otherwise opposite to those of the eye side. The 

 margin of all four is sometimes membranous and pro- 

 longed, in the case of the two posterior nostrils, how- 

 ever, onlj' slightly and sometimes almost imperceptibly. 

 In the two anterior nostrils this membranous prolong- 

 ation of the margin is so marked behind that it may 

 tall forward like a lid and cover the whole nostril. 

 At the anterior margin a small, narroAv flap may be 

 found. In young sjiecimens, even at a length of 50 

 mm., the eyes are still in a line with each other, or the 

 upper eye may even lie somewhat further forwai'd than 

 the lower. This is a trace of the eai-lier stages of de- 

 velopment, when the wandering eye tirst passed some 

 way forward and then, when it had crossed the bridge 

 of the snout, retired backwards on the eye side. In 

 older specimens, on the other hand, at a length of 53 

 cm. for example, the upper eye has sometimes moved 

 so far Ijack that its anterior mai-gin is in a line with 

 the middle of the lower eye. The eyes are fairly ecjual 

 in size, their relative size decreasing as usual Avith age. 

 In Turbots 50 mm. long the longitudinal diameter of 

 tlie lower eye is 37 or 38 94 of the length of the head 

 behind it, while in Turbots 53 cm. long this proportion 

 has sunk to about 14 %. The breadth of the inter- 

 orbital space on the wliole also undergoes relative de- 

 crease, l)ut to a much slighter extent; while until the 

 fish has attained a length of 20 or 25 cm., this breadth 

 increases not only absolutely, by growth, but in the 

 above relation as well. In specimens 20 cm. long it 

 measures about 19 or 20 % of the postorbital part of 

 the head, but in specimens 53 cm. in length only about 

 16 % thereof. In s]jecimens 50 nun. long the breadth 

 of the interorbital space is only about '/a the longi- 

 tudinal diameter of the lower eye, while in specimens 

 53 cm. long it is "/j of this dia-meter. The length of 

 the snout, measured from the anterior margin of the 

 loAver eye, is about ' '^ of that of the head. The pre- 

 operculum is rectangular, rounded at the angle, and 

 with the vertical prong about \',^ longer than the hori- 

 zontal. The operculum is triangular, like that of the 

 Codfishes, with the hind lower side concave. Into this 

 concavity the upper, narrower part of the suboperculum, 

 the rest of which is of uniform breadtli, is fitted, ex- 



tending so far that it penetrates the posterior dermal 

 flap which forms the end of the gill-cover, just above 

 the axil of the pectoral fin. The interoperculum is of 

 fairlj' uniform breadth, but as usual grows narrower in 

 front, its breadth behind l^eing about \, ,j of the length 

 of the upper jaw-bone. The branchiostegal memliranes 

 lie, as in most of the Flatfishes, in a deep fold below, 

 Avhere they meet and cross each other, most distinctlj^ 

 in old specimens. The innermost (foremost) of the seven 

 branchiostegal ravs in each membrane is not united 

 at all to the corresponding ray on the other side, as 

 we have found it in the preceding Flatfishes, but lies 

 parallel to the other rays. 



The dorsal fin is furnished with a thick skin, and 

 begins on the blind side, just above and in front of 

 the anterior margin of the anterior nostril, exactl}' fol- 

 lowing the dorsal edge throughout its length, Avithout 

 bending at all towards the blind side at its termination. 

 As a rule the 30th — 35th ray from the beginning is 

 the longest, its length being about 12',., or ll'/, of 

 that of the body. Measured in a straight line, the base 

 of the dorsal fin occupies from about Tl'/o to 74'; ^ % 

 of the length of the body. The fin contains 57 — 64 

 rays, those in the anterior haJf of the fin being gener- 

 ally simple or only indistinctly branched, while those 

 in the posterior half are branched, sometimes with a 

 simple ray inserted here and there. In 3'ouiig specimens 

 the posterior rays are also simple or indistinctly branch- 

 ed. The distance between the anal fin and the tip 

 of the snout is at least (in the males) 30 ?4 and at most 

 (in the females) 35 or 36 ?^ of the length of the body. 

 The 17th or 18th (sometimes even the 21st) rav from 

 the beginning of the fin is the longest, being generally 

 equal in length to the longest ray of the dorsal fin; 

 and to the structure of the rays the same remark ap- 

 plies as in the case of the dorsal fin, with the addition 

 that in this fin all the rays are still more frequently 

 simple. Measured in a straight line, the base of the 

 anal fin occupies about 58 — 59 '/^ % of the length of 

 the body. There is no projecting spine at the begin- 

 ning of the anal fin, which in young specimens and the 

 males is included between the posterior parts of the 

 insertions of the ventral fins, and has the vent close 

 beside it on the blind side, just behind the end of the 

 ventral fin. The genital opening lies just behind or on 

 the outer side of the vent, and in the males is furnished 

 with a small, pointed papilla at the anterior margin. 

 The urethral opening, with its more or less distinct 



