PLAICE. 



393 



28 and 2() %, sometimes as low as 25*/.. %, of the same 

 measurement. The form of the head is wedge-shaped, 

 with the snout rather tumid and with a deep depres- 

 sion in the dorsal edge at the upper eye. The chief 

 characteristic of the species consists in the row of osse- 

 ous protuberances, usually 6 in number and of differ- 

 ent sizes, that extends for\vard from the beginning of 

 the lateral line of the bod)' to the eyes. Here thej' 

 are i-eplaced by a raised, smooth, bony keel, which bends 

 down Ijetween the eyes, forming a dividing ridge be- 

 tween them, and anteriorly divides into an angle that 

 includes the posterior part of the nasal cavity of the 

 eye side, and ends in front of each eye in a more or 

 less distinct knob, most developed in front of the upper 

 corner of the lower eye. The first-mentioned pro- 

 tuberances do not all belong to the head itself. The 

 penultimate one, which is generally the largest, is situ- 

 ated on the pterotic part of the temporal bone of the 

 skull (as squamosum vel ptcrotkum), but the last of all 

 belongs to the posttemporal bone (the suspensory bone of 

 the shouldei'-girdle). The mouth is of about the same 

 size as in the last species, but the lips are more tumid. 

 The lower jaAv is somewhat prominent, the length of 

 the brunch of the lower jaw on the blind side varying 

 between about 33 and 40 % of the length of the head, 

 or during j-outh between about 10 and 9 %, and in 

 older specimens about 8 ?», of the lengtli of the body". 

 The teeth are small, in young specimens sharp and set 

 in two rows (at least in the blind side of the lower 

 jaw), l)ut in adult specimens bluntly pointed, close-set 

 incisors, set in a single row in both jaws. Their num- 

 ber varies in different individuals, both in the upper and 

 the lower jaws. In the upper jaw, on the inter- 

 maxillary bone of the blind side, we may tind from 

 19 to 3G'' teeth, and on the intermaxillary bone of the 

 eye side, from 3 to 14''. In the lower jaw the branch 

 on the blind side is furnished with from 20 to 45' 

 teeth, and that on the eye side with from 5 to 14''. 

 In front, in tlie middle of the jaws, there is a distinct 

 space between the teeth of either side. The pharyn- 

 geals, 6 above and 2 ])elow, are armed with broad, con- 

 vex teeth, set in rows. The gill-rakers are scarcely of 

 average size, and are also scattered, there being 11 or 



10, sometimes only 7, on the first liranchial arch. The 

 nostrils are situated as in the preceding species, those' 

 of the blind side Ij'ing in the middle of the deep de- 

 pression of the dorsal edge at the upper eye. But the 

 anterior nostril of the eye side is long and perfectly 

 tubular, while that of the blind side is more distinctly 

 cut in an oblique direction. The posterior nostrils are 

 like slits, in most cases with the margin more or less 

 raised in a tubular form. At tlic margin of the tubes 

 formed by the anterior nostrils Ave find, in front, a 

 small, pointed, dermal flap, which is more distinct, how- 

 ever, in the following species. The tongue is narrow 

 and pointed, as is generally the case in this genus, and 

 without teeth. The gill-openings are middle-sized, and 

 are furnished Avith 7 branchiostegal rays. The eyes are 

 generally set on the right side, seldom on the left, 

 their longitudinal diameter, in specimens of average 

 size (33—34 cm. long), being about V^ (18—21 %) of 

 the length of the head; and the lower eye is onl)- 

 slightly in front of the upper. 



The body is covered, as a rule, with cycloid scales 

 alone, which are thin and deeply embedded, contiguous 

 but not imbricated. The scaly covering extends for- 

 Avard to the eyes and along the cheek below the lower 

 eye, to the articulation of the under jaw; but on the 

 blind side the operculum and the greater portion of 

 the preoperculum are naked. Imbricated scales occur 

 on the e}-e side of the larger rays in the dorsal and 

 anal fins' and on both sides of the caudal tin. The 

 pectoral and \entral fins of the eye side are also partly 

 covered with scales, but only at the base. There is 

 one variety, however, Gottsche's Platessa Pseudoflesus 

 (1. c, p. 143) and NiLSSOx's varietas halfica, commonest 

 in the Sound and the south of the Baltic'', and known 

 at Abekas as horuuge (bastard), "because it is believed 

 to be a hybrid l)etween the Plaice and the Flounder," 

 which is distinguished by ciliated scales, as a rule only 

 on the eye side, which are imbricated even on the body, 

 and are most distinct along the lateral line and the 

 bases of the dorsal and anal fins, and on the head. 



The course of the lateral line, which is slighth" 

 arcuate above the pectoral fins, is straight from this 

 point, and fairh" closely follows the middle of the sides, 



" In very large specimens tliere is sometimes a reversion to the juvenile form. 



'' The latter niunber in a female 65 cm. long. In this case the dentition-formuUi was: 



'' Very often, however, these scales are wanting. 

 '' KrOYER fonnil this variety otf Hastholm as well.' 



Scandinarian Fishes. 



14— 36 

 U— 45' 



50 



