FLAT-FISH. 



443 



and all the head, except the muzzle, covered with minute scales ; its colour being 

 greyish brown, with reddish brown spots. Turbot commonly weigh from 5 to 

 10 lbs., and occasionally reach 20 or even 30, while considerably greater weights 

 have been recorded. Another British representative of the genus is the Mary -sole 

 (Jili. aquosus), which may be distinguished by its ciliated scales : while a fourth, 

 known as Block's top-knot (Rh. punctatus), differs from all the foregoing by having 

 the pelvic fins confluent with the anal. The true top-knot (Phrynorhombus 

 unimaculatus), which is a small form not uncommon on the southern coasts of 

 England, and abundant in the Mediterranean, is referred to a distinct genus on 

 account of the absence of vomerine teeth. A turbot is shown in the central figure 

 of the coloured Plate. 



Plaice and The plaice (Pleivronectes platessa) and flounder (PI. jiesus), of 



Flounder. which examples are shown in the right lower corner of the coloured 

 Plate, are examples of a genus pertaining to a group characterised by the narrow- 

 ness of the cleft of the mouth, and by the jaws and teeth being much more developed 

 on the light than on the dark side. Unlike the turbot and its allies, where the 

 upper is somewhat behind the lower, the two eyes are in the same transverse line, 

 and generally situated on the right side. The dorsal fin commences above the 

 eyes ; the scales are minute or wanting ; and there are no teeth on the palate, 

 while those in the jaws are of medium size, and may be arranged in either a double 

 or a single row. The genus, which is common to the Northern, Temperate, and 

 Arctic seas of both hemispheres, contains over a score of species, which may be 

 divided into groups according to the form of the teeth, the number of rays in the 

 dorsal fin, and the conformation of the lateral line. The plaice, which ranges from 

 the French coasts to Iceland, and is represented by an allied form on the opposite 

 side of the Atlantic, belongs to a group with compressed, lanceolate, or truncate 

 teeth, and no fewer than ninety dorsal rays ; it has the brownish upper surface 

 marked with bright yellow spots. This species is exclusively marine, but the 

 flounder is almost as much a fresh-water as a sea fish, ascending rivers to a con- 

 siderable distance. Distinguished from the plaice by the dark mottlings on the 

 brownish or brownish yellow skin of the upper surface, it belongs to a group in 

 which the teeth are conical ; the lateral line being very slightly curved in front, 

 and the scales minute. Its distribution is practically the same as that of the 

 plaice, and it is represented by an allied species in the Mediterranean. 



In the plaice and its allies the pectoral fins are always well 

 developed, but in the group to which the common sole (Solea vulgaris) 

 belongs these may be wanting, while the upper eye is always somewhat in advance 

 of the lower one, both being on the right side. As a genus the numerous species 

 of soles (somewhere about forty in number) are characterised by the median fins 

 being separate from one another, and the ctenoid scales ; the dorsal fin commencing 

 on the muzzle, and the lateral line being straight. The cleft of the mouth is very 

 narrow, and twisted round to the left, or blind side ; and it is on this side only that 

 villiform teeth are developed in the jaws, the palate being toothless. With the 

 exception of the lower south temperate zone, soles are distributed over all temperate 

 and tropical coasts in localities suited to their habits ; many of the species entering, 

 or even dwelling permanently in fresh waters. The common sole, which is found 



