The animals of this order, commonly known as sand-cakes or sand-dollars, are flat and circular like disks. Sometimes they are cut at intervals on the margin; again they have slits through the body (/lunules/). They have a well-marked star-shaped figure on the dorsal surface. This figure is formed by the ambulacra, or tube-feet, which run in five rounded or petal-shaped lines on the under surface. The mouth, in Aristotle's lantern, is in the center of the somewhat concave ventral surface, the petal-like ambulacral zones meeting at the central space. The excretory opening is on the margin of the disk, at a point between two of the sections of the star-like figure. This marks the posterior part of the body, while the opposite arm of the star marks the front or anterior end. The spines are very fine and silky, and are spread abundantly over the whole animal. Clypeasteroids are mainly found in sand considerably below low-water mark, though some species thrive where they are exposed to the surf on open sandy beaches. FAMILY ~ECHINANTHIDÆ~ GENUS ^Clypeaster^ ^C. ravenellii.^ This species occurs in deep water from South Carolina southward. The disk is about four inches in diameter, and is raised [pg225] in the center into a large cone. The ambulacra run down the sides of the cone in straight lines, and around the base is a depressed area which emphasizes a thick border which extends around the scalloped margin. The color is light yellowish-brown. (Plate LVIII.) GENUS ^Echinanthus^ ^E. rosaceus.^ This is a large species, oblong in shape, about four to five inches across and much rounded on top, the body being about two inches thick. The ambulacral zones are depressed, leaving prominent elevations which make a very conspicuous figure on the top. The color is light chocolate-brown. Found close to the shore off the coasts of Florida, South Carolina, and the West Indies. FAMILY ~SCUTELLIDÆ~ GENUS ^Echinarachnius^ THE SAND-DOLLARS ^E. parma.^ This species, the shells of which are very common objects on sand-beaches from New Jersey northward, is generally known as the sand-dollar. The animals have flat circular disks about three inches in diameter. The ambulacral zones, in five petal-like lines, form a distinct figure on the upper surface. The mouth is in the center of the ventral surface, and the excretory opening is on the edge of the disk. In life they are covered with short, fine, silky spines, which seem like hair, and are purplish-brown in color, but turn green when taken from the water. The sand-dollars are exceedingly abundant off Nantucket Shoals, where the bottom seems paved with them. They are eaten in great numbers by flounders, cod, and haddock. When put in alcohol they stain it a dark color. Fishermen prepare an indelible ink by grinding to powder these animals and mixing it with some liquid. This species is also found on the northern Pacific coast.