370 
SCANDINAVIAN FISHES. 
and in the Flatfishes is extraordinarily well-developed 
and together with the hrnmal spine of the first caudal 
vertebra, on the front of which it is supported at the 
top, forms the curved hind wall of the abdominal cavity, 
which is comparatively narrow in these fishes. 
The abdominal cavity is at first comparatively long, 
the vent in the larva? when just hatched, sometimes 
lying even behind the middle of the body. But during 
the course of development the vent is moved farther 
and farther forward, while the abdominal cavity is 
relatively shortened until in full-grown specimens it 
becomes more or less semicircular in its median longi- 
tudinal (sagittal) section. The vent thus assumes a very 
forward position, and in many forms lies at the middle 
of the ventral margin; but in the most distorted types 
it passes over to the blind side. The greater part of 
the left side of the abdominal cavity is occupied by 
the liver, around which, above and behind, lie the 
oesophagus and the stomach, which is only slightly 
divided from the latter, behind and below, the in- 
testine. The intestine usually forms an immediate con- 
tinuation of the stomach, being sharply divided from 
the latter internally by a very muscular, funnel-shaped 
pylorus, below which hang the pyloric appendages, 
which are few and, in most cases, small. To the right 
of the abdominal cavity lie the coils of the intestine, 
attached to the mesenterium, with its numerous and 
large, lymphatic vessels. Here too, we find the spleen 
and the gall-bladder, which is generally large. The 
kidneys are, as usual, situated in the abdominal cavity, 
just under the spinal column, and the ureters are united 
into a urinary bladder. The organs of generation lie 
at the middle of the hind wall of the abdominal cavity; 
but when they are much developed and tumid, the 
space allowed for them within the abdominal cavity is 
too small, and they force their way back, in a flat, 
conical shape, between the large muscles of the body 
and the interhaemal bones of the anal fin or the lnemal 
spines of the caudal vertebra?, on each side of the 
latter. 
The family of the Flounders is one of those with 
the most numerous species. Gunther in Ins Catalogue 
of 1862 gives the number of species in this family as 
229, distributed among 34 genera; while in 1883 .Tor- 
dan and Gilbert recognised nearly 400 species * * 3 4 * . In 
his Introduction to the Study of Fishes (pp. 553 — 559) 
Gunther gives 42 genera. 
The geographical range of the family embraces all 
the seas from the Equator to the Polar Regions; and 
some of the species even make their way into fresh 
water. The greatest abundance of forms belongs, it is 
true, to the tropical seas; but the largest species belong 
to temperate and cold climates. The family is repre- 
sented even off Bear Island and Spitsbergen. 
On account of the great variety of forms a sub- 
division of the family is quite necessary. At the time 
when the general signification of the genus corresponded 
to the family of modern ichthyologists, a division of 
this nature was proposed by Quensel 6 , who broke up 
the old genus Fleur onectes into two genera: Fleur onectes, 
“with the mouth at the tip of the head and furnished 
with distinct, movable jaws, the lower being longer or 
more prominent than the upper,” and Solea, in which 
“the mouth is crescent-shaped, set obliquely at the 
sharp edge of the under margin of the head, and furn- 
ished with indistinct jaws, the upper being prominent 
and longer than the lower.” According to the same 
character in all essential respects Bonaparte/ distin- 
guished between the subfamilies Pleuronectini, “ in cui 
la mascella piu lung a e Vinferiore,” and Soleini, “in cui 
la piu lung a e la superior e” . Gunther'' also di- 
vided the family of the Flounders into two groups: 
I, with the jaws and their teeth almost equally de- 
veloped on each side of the body, and II, with narrow 
mouth, in which the teeth are more developed on 
the blind side than on the eye side. Thus we al- 
ready have a suggested principle on which to arrange 
this family in three subfamilies. Furthermore, Gill 
soon afterwards 6 quoted Cuvier’s distinction between 
the subgenera Hippoglossus and Bhombus, and on the 
strength of the structure and position of the ventral 
fins in the latter genus established the subfamily Bhom- 
bince. Thus we now have fixed characters for four 
subfamilies: 
a The number of the species cannot be fixed exactly. 
6 Vet.-Akad. Handl. 1806, pp. 44 and 203. 
c Icon. Fri. Ital., tom. Ill Pleuronectes macrolepidotus , nuin. p. 22. Cf. also Bleeker, Atl. Ichthyol. Ind. Neerl., tom. VI, pp. 
4 and 16. 
d Brit. Mus. Vat. Fish., vol. IV, p. 400. 
e Proc. Acad. Nat. Sc. Phil. 1864, p. 215. 
