BRITISH FRESH- WATER FISHES
Flounder.—Pleuronectes flesus (Fig. 64). This, the last species which it is desirable to include in our list of fresh- water fishes, migrates considerable distances up-river, and although there are many other species of marine fishes which frequent brackish and even fresh water, there is not much amiss with the selection that has been made in this volume, and the Flounder is certainly entitled to inclusion in preference to several others. It is, as is well known, one of the flat-fishes, having an ovate body, with an array of fins extending at least three-fourths of the whole. The body is covered with small scales, and along the inside length of the dorsal and ventral fins there is a row of spinous tubercles, as also a little group at the head end of the lateral line. The general colour is greyish-olive, but there is considerable variation, and one writer says " it varies from nearly yellow to almost black." In some specimens there are orange spots, as in the Flounder's nearest relative, the Plaice I^eft-sided, as well as right-sided, examples are frequendy forthcoming, as also specimens coloured alike on both sides. It resorts to shallow water close inshore and delights in a sandy bottom. Although of sluggish habits, it regularly ascends a number of our rivers, and when swimming, its movements are most fascinating to watch. When I was on Loch Lomond in the Autumn of 1922 a Flounder was captured in the famous Loch, the first that had been known to appear there for over twenty years. The food consists of crustaceans, molluscs, worms, and small fishes. The spawning time is of ex-
