The New Student's Reference Work/Sand-Dollar
Sand-Dol′lar, the name given to a flattened sea-urchin, very common on sandy shores. The soft parts are inclosed in a rounded, flattened disc, made of plates of carbonate of lime nicely fitted together. When living, the discs are covered with short spines. They are dark-yellow or whitish if bleached in the sun. There are five rows of plates with minute holes for the tube-feet as in other sea-urchins, and five rows without holes. In certain forms the disc is completely perforated by a number of orifices of a key-hole pattern. See Sea-Urchin.