PETROMYZON, the lamprey, in natu ral history, a genus of fishes of the order Cartilaginei. Generic character : body shaped like an eel ; mouth beneath, with numerous teeth, in circular rows ; seven spiracles on each side the neck ; no pec toral or ventral fins. Shaw notices nine species, and Gmelin only four. P. mari nus, or the great lamprey, is usually of a brown olive colour, tinged with yellowish white. It is often three feet long ; is an inhabitant of the seas, as its name indeed implies ; but in the beginning of spring ascends rivers, in which it resides for a few months, then returning to the ocean. It is viviparous, and supposed to subsist almost entirely on worms and fishes. Its heart is enclosed not in a soft but in a car. tilaginous pericardium, constituting thus a singular deviation from the general structure of animals. Its spine also pos sesses the peculiarity of being rather a soft cartilage than bone. These fishes fasten themselves with the jagged edges of the mouth to large stones, with the most extraordinary firmness, and may be lifted by the tail to a considerable height, without being made to quit a stone of the weight of even ten or twelve pounds. Their principle of vitality is extremely vi gorous and persevering, various parts of the body long continuing to move for some hours after it is divided ; and the head will adhere to a rock for hours after the greater part of the body is cut away. In some large rivers of Europe, these fishes are taken in vast numbers, and pre served with spices and salt as an article for merchandise. In England, the Severn is the most celebrated river for them, and they are much valued on their first arri val from the sea. They are considered a
high luxury fur the table, and the life of one of the Kings of England will be recol. lected to have been terminated by his ex cessive partiality to potted lampreys.
P. fluviati!is, or the lesser lamprey of Europe, is about twelve inches long, in habits also the sea, but is found more frequently in the rivers than the former. It abounds in the Thames and Severn, and is preferred by many to the larger species, as being not so strong in taste. In some years half a million of these fishes have been sold from the neighbourhood of Mortlake, for the Dutch cod and turbot fishery, at the rate of two pounds per thousand. In many parts of Germany they are fried and packed up in barrels with spices and bay leaves, and are con. veyed to very distant regions, where they are in high estimation, and sell for consi derable prices. These fishes will live ma ny days out of the water. In Riissia they are taken from beneath the ice, pack ed in snow, and exported to great dis. tances, and will generally recover them. selves on being afterwards thrown into the water. The planer lamprey is ten inches long, will live immersed in spirits of wine for fourteen minutes, moving dur ing that time with incessant violence. The leech lamprey is a native of the ris. ver Seine,and will fix on the bellies of va.
lions fishes, particularly the shad, suck ing their blood,