Some sea-fish are flat, such, for instance, as the rhombus,[2448] the sole,[2449] and the sea-sparrow;[2450] which last only differs from the rhombus in the lateral position of the body. The rhombus lies with the right side upwards,[2451] while in the sea-sparrow the left side is uppermost. Some sea-fish, again, are long, as the muræna and the conger. CHAP. 37.—THE FINS OF FISH, AND THEIR MODE OF SWIMMING. Hence it is that there is a difference,[2452] also, in the fins of fish, which have been given them to serve in place of feet, none having more than four,[2453] some two[2454] only, and others none.[2455] It is in Lake Fucinus[2456] only that there is a fish found that has eight fins[2457] for swimming. Those fishes which are long and slimy, have only two at most, such, for instance, as eels and congers: others, again, have none, such as the muræna, which is also without gills.[2458] All these fish[2459] make their way in the sea by an undulatory motion of the body, just as serpents do on land; on dry land, also, they are able to crawl along, and hence those of this nature are more long-lived than the others. Some of the flat-fish, also, have no fins, the pastinacæ,[2460] for instance—for these swim broad-wise—those, also, which are known as the “soft” fish, such as the polypi, for their feet[2461] serve them in stead of fins. CHAP. 38. (21.)—EELS. Eels live eight[2462] years; they are able to survive out of water as much as six days,[2463] when a north-east wind blows; but when the south wind prevails, not so many. In winter,[2464] they cannot live if they are in very shallow water, nor yet if the water is troubled. Hence it is that they are taken more especially about the rising of the Vergiliæ,[2465] when the rivers are mostly in a turbid state. These animals seek their food at night; they are the only fish the bodies of which, when dead, do not float[2466] upon the surface. (22.) There is a lake called Benacus,[2467] in the territory of Verona, in Italy, through which the river Mincius flows.[2468] At the part of it whence this river issues, once a year, and mostly in the month of October, the lake is troubled, evidently by the constellations[2469] of autumn, and the eels are heaped together[2470] by the waves, and rolled on by them in such astonishing multitudes, that single masses of them, containing more than a thousand in number, are often taken in the chambers[2471] which are formed in the bed of the river for that purpose. CHAP. 39. (23.)—THE MURÆNA.