e ki'no dur'mah tah, the third from the lowest of the seven great branches into which the animal kingdom is divided. Sometimes the echinoderms are grouped together, but each animal leads its individual life. The five parts of nearly all are arranged on a radiating plan something like the spokes of a wagon wheel, this at one time giving them the name Radiata and causing this class to include the Coelenterata. In some species the covering of the echinoderms is a soft, leathery sack, but in others it is a hard shell. The alimentary canal is separate from the body cavity and bones above and below. Motion and the few special senses are governed by a well-organized nervous system. Around the mouth of the animal is a ring-like vessel which is connected with organs in various parts of the body. This constitutes the water vascular system, by which locomotion and breathing are conducted. Water is taken into the ring and carried thence into minute organs called ambulacra, or short tubular "feet," which are thus thrust forward and outward, in the case of the shelled echinoderms, through small pores in the shell. Generations alternate, the egg from the mature animal producing a free-swimming form which differs decidedly from the adult form that grows out of it. There are about 3000 living species found in all the seas of the globe, but they are most abundant in tropical seas. See SEA URCHIN; STARFISH; CRINOIDEA.