^S. drobachiensis.^ This sea-urchin (which bears, perhaps, the longest name in technical nomenclature and has no other, unless that of "sea-egg," which is applied indiscriminately to all sea-urchins) is a very common species in shallow waters of the northern temperate zones. It extends as far as New Jersey on the Atlantic and to the State of Washington on the Pacific coast. Although it is found as far south as New Jersey, it is there rare and small; but farther north, especially on the coast of Maine, it is exceedingly abundant. It is green or greenish-purple in color, and resembles somewhat a large chestnut-bur. The body is circular, somewhat depressed (but of variable thickness), and about two inches in diameter. The spines are moderately slender and longitudinally striated. It feeds partly on diatoms and other small algæ, which it cuts from the rocks with its sharp teeth. It also devours dead fishes, bones and all, and in return is swallowed whole by the wolffish and other large fishes. It moves by means of the tube-feet on its oral surface, slowly dragging itself along, and frequently is seen with seaweed, a stone, or some other substance on its back, which it places there with its pedicellariæ for the purpose of concealment. ^S. purpuratus.^ The common purple sea-urchin of the west coast, from Sitka to Lower California, found in abundance on the rocks just beyond low-water mark. It is about one and a half inches in diameter, with rather thick, pointed, and fluted spines. ^S. franciscanus.^ This is the largest species of the west coast, the shell measuring sometimes five inches across, and the thick spines one and a half inches in length. The tubercles on the naked shells are very prominent, and the zones are very clearly marked. It is purple in color and is often found in great quantities at low-water mark. It ranges from Alaska to Lower California. (Plate LVII.) FAMILY ~ECHINIDÆ~ In this family the ambulacral plates have but three pairs of pores. [pg224] GENUS ^Echinus^ ^E. gracilis.^ This is a deep-water species, which occurs from Cape Cod southward. The shell is nearly spherical, but is a little depressed on the oral side, and has twenty bands of color, alternately green and white. The spines are short and thin. GENUS ^Toxopneustes^ ^T. variegatus.^ This is the common species of the Southern States, from North Carolina southward, and is found in shallow water in protected places. The shell is nearly globular; the spines vary in thickness and color, some being long, slender, and greenish, while others have stout and blunt spines of a yellowish or violet tint. ORDER =CLYPEASTROIDEA= CAKE-URCHINS