40 M.ATFISHKS (HI-/H-:K( )SC)M.\T.\) 



With the exception of the genera of Khonibosoleiiue already lueiitiuiieil, in all the 

 I'leiironei tidic the nasal organ of the blind side has accompanied or followed the eye 

 in its migration and lies nearly on the edge of the head. The taxononiic importance 

 of the position of the first ray of the dorsal fin with relation to this nasal organ has 

 been dealt with at some length by Kyle (1900B). In the Pleuronectina? and the 

 closely related Pircilopsettinae the origin of the fin is behind the nasal organ of the 

 blind side and above the "upper" eye. In the two subfamilies Samarina? and Para- 

 lichthodma; the fin extends forward in front of the eye to the .snout, in the fir.st sub- 

 family below the nasal organ of the blind side, in the second above it. In the last 

 subfamily, Khombosoleina?, in the more generalised forms the dorsal fin commences 

 behind the nasal organ as in the PleuronectiUce, but in other genera it extends forward 

 on the snout above the nasal organ. 



The pelvic fins in the I'leuronectida; (Fig j^) are usually short-based and supported 

 by the jielvic bones behind or below the clcithra. In the l'leuronectin:r and Piecilop- 



-'1.— Pectoral .irrh .ind pelvic hones of a. /■;, 

 nov.e zedandue ( • ij); c, RhnmhmaU,, plchc 

 ui Fir. 2i. [Froii, Mind si.le.i 



settina? {\) the two fins arc more or less symmetrically placed, but m the I'araluh- 

 thodina' and Samarina- that of the ocular side is situated on the median line and is 

 somewhat in advance of that of the blind side (b). In the Rhombosoleinae the pelvic 

 fin of the ocular side is median, elongate, extends forward to the urohyal, and is 

 supported by a cartilaginous plate placed in advance of the cleithra. In five of the 

 eight known genera of this subfamily this fin is united with the anal.' In most of the 

 genera the pelvic fin of the blind side is also developed, but this is much smaller and 

 has a base which is short or of moderate length. In Rhombosolea (c), however, only 

 the pelvic fin of the ocular side is present. - 



The pectoral arch provides two characters which may be used to distinguish the 

 subfamilies of Pleuronectidae. In the Pleuronectina', I'a'cilopsettina?, Samarina; and 

 Paralichthodinae pectoral radials are present, but in the RhombosoleinEe these are 



^ The presence of an elongate pelvic 

 to a fish which relies upon undulating n 

 this extends forward to below the jaws, 

 body of the tish is surrounded by practK 



- Except sometimes in reverscil exaii 



the ; 



line presents a mechanical ad\'antage 

 ■nts of the marginal fins to aid progression. When 

 united posteriorly with the anal, the whole of the 

 mtinuous fins — dorsal, caudal, anal and pelvic. 

 ,ee p. 2;). 



