The scientific name for the lampreys is “_Petromyzon_,” a word signifying “stone-sucker”. The name is rightly applied; for when the lampern wishes to remain still in one place, it applies its mouth to a stone, sticks tightly to it by suction, and there remains firmly at anchor, and defying the power of the stream. In favourable spots, thousands of these fish may be seen together, quite blackening the bottom of the stream with their numbers. They seem specially to affect shallow mountain streams; and, in spite of the rapid current, wriggle their devious way up the stream with great rapidity. When they are not quite pleased with the spot on which they settle down for the time, they scoop it out to their minds in a very short time. This task is accomplished by means of the sucker-like mouth. If a stone is placed in a position that incommodes them, they affix their mouths to it, and drag it away down the stream. In this way they will remove stones which are apparently beyond the power of so small a creature. By perseverance they thus scoop out small hollows, about eighteen inches long and a foot wide, in which they lie in groups so thick that I have more than once mistaken them for dark logs lying in the stream, and was only undeceived by the waving of the multitudinous tails. Year after year the lamperns followed the same course, and chose the same positions, so that we could at any time tell where these creatures would be found by the thousand, where they would be found singly, and where none would be seen at all.
The general thickness of this creature is that of a large pencil, but it varies according to the individual. The length is from one foot to fifteen inches or so.
There is a much smaller species of lampern called the Pride, Sand-pride, or Mud Lamprey, which is not more than half the length of the lampern, and only about the thickness of an ordinary quill. This creature has not the power of affixing itself like the lampern, on account of the construction of its mouth.
Having now taken a hasty glance at the vertebrated animals, we pass to those who have no bones at all, and whose skeleton, so to speak, is carried outside. Our representation of aquatic crustacea, as such creatures are called, will be the Cray-fish and the Water-Shrimp.