;70 



SCANDINAVIAN FISHES. 



iiufl ill the Flatfishes is oxtrMordinarily well-developed 

 and together Avith the htenial si)iae of the tirst caudal 

 vertebra-, on the front of \vhicli it is supported at the 

 top, foriDS the curved hind wall of the abdominal cavity, 

 which is comparatively narrow in these tishes. 



Tlie abdominal cavity is at first comparatively long, 

 the vent in the larvae when just hatched, sometimes 

 lying even behind the nuddle of the body, liut during 

 the course of development the vent is mo\'ed farther 

 and farther forward, while the abdominal cavity is 

 relatively shortened until in full-grown specimens it 

 becomes more or less semicircular in its medinn longi- 

 tudinal (sagittal) section. The vent thus assumes a very 

 forward position, and in many forms lies at the middle 

 of the ventral margin; Init in the most distorted types 

 it passes over to the l)]ind side. The greater part of 

 the left side of the abdominal cavity is occupied by 

 the liver, around \vhit'h, al>ove and behind, lie the 

 (esophagus and the stomach, which is only slightly 

 divided from the latter, behind and l)elow, 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 



of 186'2 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". In 

 his Introduction to the Stiidi/ of Fishes (pp. .3.53 — 559) 

 GuNTHER gives 42 genera. 



The geographical range of tlie familv embraces all 

 the seas from the Equator to the Polar Regions; and 

 some of the species even make their way into fresh 

 watei'. 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 Spitzbergen. 



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 l)y Quensel', who broke up 

 the old genus Pleuronectes into two genera: Pleuronectes, 

 "witli the mouth at tlie tip of the head and furnished 

 with distinct, movable jaws, the lower being longer or 

 more prominent than the u])per," and Solea, in which 

 "the mouth is crescent-shaped, set obliquely at the 

 sharp edge of the under margin of the head, and furn- 



pylorus, below which hang the pyloric ap])endages, | ished M'ith indistinct jaws, the upper being prominent 

 which are few and, in most cases, small. To the right j and longer than the lower." According to the same 

 of the abdominal cavity' lie the coils of the intestine, character in all essential respects Bonaparte' distin- 



attached to the mesenteriuin, 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; 

 liut 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 interhajmal bones of the anal fin or tlie h;\?raal 

 spines of tlie caudal \ertebr8e, on each side of the 

 latter. 



Tlie family of the Flounders is one of those with 

 the most numerous species. Gunthei! in his Catnlof/iie 



guished between the subfamilies Plenroiiecfini, ''in- ciii 

 la masceJIn pin litnga e l"nifeyi<)ii\' and Soleini, ''in cui 

 1(1 piii hiiifia e la sKperiore\ Guxtiier'' also di- 

 vided the family of the Flounders into two groups: 

 I, Avith tlie jaws and their teeth almost equallj' 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^ quoted Cuvier's distinction between 

 the subgenera. Hippoglossus and Bhomlms, and on the 

 strength of the structure and position of the ventral 

 fins in the latter genus established the subfantily Bhoiu- 

 hince. Thus we now have fixed characters for four 

 subfamilies: 



" The number of tlie species cannot be fixed exactly. 

 * Vet.-Akad. Handl. 1806, pp. 44 and 203. 



'■ [coil. Fit. Jtiil.. tdiii. Ill Pleuronet-te.-i iiuicrolepidolii.i, nnm. p. H. Cf. also Bi.EEKicn. .1//. Ichthijol. lad. Accrl., torn. VI, pp. 

 4 and IG. 



•' nrit. ^flts. Vat. F/.s-//., v(.l. IV, p. 400. 

 ' Proc. Acad. Nat. Sc. Pbil. 18G4, p. 215. 



