PLAICE, 
393 
28 and 26 %, sometimes as low as 25 x / 2 %, 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 forward from the beginning of 
the lateral line of the body to the eyes. Here they 
are replaced by a raised, smooth, bony keel, which bends 
down between 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 (os squamosum vel pteroticum), but the last of all 
belongs to the posttemporal bone (the suspensory bone of 
the shoulder-girdle). The mouth is of about the same 
size as in the last species, but the lips are more tumid. 
The lower jaw is somewhat prominent, the length of 
the branch of the lower jaw on the blind side varying 
between about 33 and 40 % of the length of the head, 
or during youth between about 10 and 9 %, and in 
older specimens about 8 %, of the length 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), but 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, avc may find from 
19 to 36 * * * 6 teeth, and on the intermaxillary bone of the 
eye side, from 3 to 14 6 . In the lower jaw the branch 
on the blind side is furnished Avith from 20 to 45 h 
teeth, and that on the eye side Avith from 5 to 14 \ 
In front, in the middle of the jaws, there is a distinct 
space betAveen the teeth of either side. The pharyn- 
geal s, 6 above and 2 beloAv, are armed Avith broad, con- 
vex teeth, set in toavs. The gill-rakers are scarcely of 
average size, and are also scattered, there being 11 or 
10, sometimes only 7, on the first branchial arch. The 
nostrils are situated as in the preceding species, those 
of the blind side lying 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 Avith the margin more or less 
raised in a tubular form. At the margin of the tubes 
formed by the anterior nostrils Ave find, in front, a 
small, pointed, dermal flap, Avhich is more distinct, hoAV- 
ever, in the folloAving species. The tongue is narroAv 
and pointed, as is generally the case in this genus, and 
Avithout 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 x / 5 (18 — 21 %) of 
the length of the head; and the loAver eye is only 
slightly in front of the upper. 
The body is covered, as a rule, with cycloid scales 
alone, Avhich are thin and deeply embedded, contiguous 
but not imbricated. The scaly covering extends for- 
ward to the eyes and along the cheek beloAv the loAver 
eye, to the articulation of the under jaAv; but on the 
blind side the operculum and the greater portion of 
the preoperculum are naked. Imbricated scales occur 
on the eye side of the larger rays in the dorsal and 
anal fins 0 and on both sides of the caudal tin. The 
pectoral and ventral fins of the eye side are also partly 
covered Avith scales, but only at the base. There is 
one variety, hoAvever, Gottsche’s Platessa Pseudoflesns 
(1. c., p. 143) and Nilsson’s varietas baltica , commonest 
in the Sound and the south of the Baltic 07 , and knoAvn 
at Abekas as honing e (bastard), “because it is believed 
to be a hybrid between the Plaice and the Flounder,” 
Avhich is distinguished by ciliated scales, as a rule only 
on the eye side, Avhich 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, Avhich is slightly 
arcuate above the pectoral fins, is straight from this 
point, and fairly closely folloAvs the middle of the sides, 
“ In very large specimens there is sometimes a reversion to the juvenile form. 
14 — 36 
0 The latter number in a female 65 cm. long. In this case the dentition-formula was: . 
& 14—45 
c Very often, however, these scales are wanting. 
d Kr0YER found this variety off Hastholm as well' 
Scandinavian Fishes. 
50 
