Ta dreiging oe oftentim source are gene, Hy impaired by c A dredge should Lot be too large, p across the mouth. The frame is ad an inch in width and an eigi th of an huet, dy that edge of which should be hammered sobour Thus ends our history of these cancrine crustacea, as the naturalists call them, namely, the crabs. Our hope has been that the reader does not regard it as crusty, cancer-ous, or crabbed. SHELL DREDGING. BY EDWARD S. MORSE. A STRONG arm and an immunity from sea-sickness are among the important requisites of a good dredger. To one who has pulled up a well-filled dredge from fifteen or twenty fathoms, the necessity of a strong arm is obvious, especially if this act has been attended with the not unusual accompaniments of a rough sea, and a cold breeze which stiffens the fingers while grasping the wet rope. One can only pity those who are sea-sick, for they are helpless. In dredging one oftentimes enjoys the keenest pleasure, attended with the greatest bodily discomforts. The miseries we will not mention. The delights come when the contents of the dredge are sifted, and there lies before you the only treasures of the deep; treasures that can be obtained in no other way. It is true that many deep-water species of shells are obtained from the stomachs of the haddock, cod and other fishes, particularly from the haddock, which seems to live principally on mollusks. Specimens procured from this source are generally impaired by the action of the juices of the stomach. The beauty of dredging consists in getting the objects in their living condition; and then you may keep them alive in sea-water for some time, and see them crawl about and watch their singular ways. A dredge should not be too large, perhaps sixteen inches across the mouth. The frame is made of a flat bar of iron, an inch in width and an eighth of an inch in thickness, one edge of which should be hammered sharp and turned out, to form the scraping edge, as represented in the cut at the close of this article. The other edge must be drilled with small holes an inch apart, to which a stout cloth bag is to be sewed. It is well to have the sides of the bag made of netting so that the water may drain from it quickly. The iron shanks are to be fastened to the dredge, as shown in the figure. A dredge of this shape, however it falls, when drawn slowly along, is sure to scrape up the mud. It is well to have for a rope a good strong one of manilahemp, and this should be well secured to the dredge. It is necessary to have the length of the rope more than twice the depth you intend to dredge in; thus, if you were to dredge in ten fathoms, you should be provided with at least twenty-five fathoms of rope, as it is necessary to give the dredge sufficient "slack" in order that it may drag properly. Should the dredge meet with any obstacle, it can generally be liberated by retracing the track passed over, dragging the dredge in an opposite direction. It is well to add that a row-boat is best to dredge from, that is for light dredges, as you want to move very slowly through the water. A fine sieve is necessary to sift out the mud, a few pails in which to empty the contents of the dredge, and some large-mouthed vials in which to save the animals alive. After a little experience in dredging you will notice that certain species live on certain "bottoms." Thus, if your dredge comes up filled with mud, you must sift the mud carefully, and from it you will find certain forms different from those you may dredge from a sandy bottom. It is well to examine your sieve often, that the smaller species may not be washed away. Sometimes the dredge will come up filled with stones; do not throw these away in disgust, but examine each stone carefully, and clinging to them you will find several species of shells found in no other way. One species, called Cemoria Noachina (Pl. 4, figs. 2, 3), is like a very small limpet, with a little hole in its top from which radiate little ribs, giving the shell a very elegant appearance. |