340 PECULIARITIES OF PLAICE FROM DIFFERENT FISHING GROUNDS. 



is liiglier in the llouuder than in the plaice, and is reduced in the 

 Baltic ; in this respect the niodilication does reduce the difference 

 between the species, and the difference in the coloration is also reduced 

 in the ]>altic. The length of the caudal peduncle in the llounder is 

 reduced in the Baltic, while in the plaice it is somewhat increased. 

 The three modifications which are in the same direction are those which 

 take place in passing from south to north; and it is a fact that the 

 Baltic is colder than the North Sea. On the other hand, it seems to me 

 probable that as the Baltic is fresher than the North Sea the flounder 

 there may live less in the rivers, and therefore, on the whole, in Salter 

 water, while the plaice lives in fresher, and that this may have some- 

 thing to do with the brighter red spots in the llounder in the Baltic. 



Tlie flounder in the Mediterranean has been described under different 

 names in the belief that it formed distinct species. The synonyms, or 

 names given to these local forms, are : — 



Plcuroncdes luscus, Pallas, Zoogr. llosso-Asiat. iii. p. 427. 1811 

 (Black Sea). 



Flatessa rjlahra, Rathke, Fauna der Krym., p. 352. 1837 (Crimea). 



Flatcssa 2JCisser, Bonaparte, Fauna Italica, Pesc. 1838-40. 



Pleuronedes italicns, Giinther, Cat. Fish. Brit. Mus. iv. 1862 

 (Dalmatia). 



I have not taken the trouble to go through the descriptions given by 

 the authors cited, but have examined the specimens in the British 

 Museum, details of whose characters are given in the lists below. The 

 chief peculiarity of italicus, according to Giinther's description, is that 

 the lateral line is smooth, not furnished with thorny tubercles. In the 

 smallest of the three specimens from Dalmatia there were no tubercles 

 on the lateral line, and no spinules on the scales on the middle fin-rays 

 of the dorsal and ventral fins. In the next specimen in order of size 

 there were spinules on 22 of the dorsal and ventral rays, no tubercles 

 on the lateral line or on the head. In the third specimen two tubercles 

 were found at the anterior end of the lateral line, but only one spinule 

 was detected on the dorsal fin, none on the ventral. Spinules on the 

 fins are not present in the North Sea flounders. The number of the 

 fin-rays is not greater than in the North Sea flounders, but is as great, 

 and therefore greater than in the flounders of the Baltic. The height 

 of body also resembles that of the North Sea specimens, while the 

 length of the caudal peduncle is as short as in the Baltic. The length 

 of head shows nothing remarkable. 



Of the local form described as luscus there were seven specimens in 

 the British Museum : four from Constantinople and the Bosphorus, 

 three from the B>lack Sea. In all these there were a number of 

 tubercles along the front part of the lateral line, but these were not 



