salt-marshes, the banks being sometimes completely honeycombed and undermined by them. It ranges from Cape Cod to Florida. [pg284] FAMILY ~MAIIDÆ~ The members of this family are known as "spider-crabs." Their bodies are thick and more or less round in form, narrowing in front to a long, beak-like projection. The surface is generally rough and irregular, having tubercles, spines, prickles, and hairs. The legs are long. These crabs are often covered with seaweeds, hydroids, and other organisms, which they gather with their long and flexible chelipeds and place upon their backs, presumably to conceal themselves from their enemies. They seem to select, instinctively or with reason, such things as will bear transplanting, sometimes using sponges and polyps which are not destroyed by being torn apart, and they also select their dress with reference to its masking uses. A /Hyas/ covered with bright-colored algæ was seen to remove them and replace them with sponges, when transferred to the locality of the latter, where the former did not grow. The animal takes in his claw the object he has gathered, and first holds it to his mouth, where it is moistened with a secretion of mucus or cement, and then places it on his back. If it does not hold, the operation is repeated, often several times, a new spot on the shell being selected each time. It has also been found that the coats of these crabs are covered with hairs which are differently arranged in different genera, some being hooked, others serrated, etc., and that these aid in holding the transplanted organisms in place. The crab is sometimes so covered with these growths as to be entirely concealed beneath them. It is a sluggish animal, and inhabits shallow water along the whole of the Atlantic and Pacific coasts. GENUS ^Libinia^ ^L. dubia^, ^L. emarginata^. These two species inhabit the Atlantic coast, and are found on muddy shores and flats, among decaying seaweed, in eel-grass, and even beneath the surface of the mud. They are covered with hairs, and sometimes have planted on their backs algæ, hydroids, and even barnacles. The legs of /L. emarginata/ often spread a foot or more. The males are much larger than the females. The species ranges from Maine to Florida. /L. dubia/ does not extend north of Cape Cod. It is found more commonly than /L. emarginata/ in very shallow water [pg285] near shore. It is not so thickly covered with spines, and has a longer rostrum, which is also more deeply divided at the end. (Plate LXIII.) GENUS ^Hyas^ ^H. coarctatus^, the toad-crab. This species of spider-crab is found from Greenland to New Jersey, in shallow as well as in deep water. Its body resembles strongly, both in form and size, that of a toad, hence its common name. It forms an important part of the food of the cod. ^H. lyratus.^ A toad-crab of the Pacific coast, ranging from Bering Sea to Puget Sound; named from the lyre-shape of its carapace.