Starfishes are voracious creatures which feed for the most part upon mollusks, including such large bivalves as oysters. The manner in which they accomplish this apparently impossible feat is very remarkable. By means of the suckers at the ends of the tube-feet the starfish attaches part of its arms to each valve of the oyster and by a steady continuous traction sooner or later so weakens the adductor muscle of the latter that the valves gape open. As the mouth is too small to admit the body of the oyster the stom ach is protruded and, enwrapping its prey, the soft body is gradually sucked through the mouth. Small gastropods may be taken into the mouth entire. Many species of starfishes lives on the bottom in vast shoals, and, although sluggish creatures, they often migrate to new feeding grounds, moving over the ground steadily in a definite direction.
The best-known starfishes of our Atlantic shores are the Asteracanthion vulgaris and A. forbesu, the former chiefly north, the latter south of Cape Cod, though both are found in Vineyard Sound and the neighboring waters. They are nearly alike, reach a diameter of 12 or 15 inches and extend from low water to considerable depths. Both species congregate in great numbers on mussel and oyster beds, often committing great havoc on the latter. They are removed from the latter by the boat load by means of dredges and tangles and cast ashore. Formerly the oystermen broke them into pieces, which were cast into the water in expectation of killing them, with the result that their numbers were increased greatly. The smooth starfish (Cribrella sanguinolenta) is a very pretty, small, shallow water species with five long, round, nearly smooth arms and a color which varies from purple to yellow and pink. It
is most abundant north of Cape Cod and is remarkable in utilizing the sides of the mouth as a brood pouch in which the young are car ried. Echinaster sentus is a related southern species with rough spinous arms. Croosaster pap possus is common in a few fathoms of water on the New England coast. It has a very broad body disc and flattish arms, which vary from 12 to 15 in number. Luidia clathrata and As tropecien articularis are flat, very brittle, five rayed starfishes with the upper surface very densely covered with small spines and the arms margined with large plates and a fringe of spines. Both occur on the south Atlantic coasts, occasionally as far north as New Jersey. Many interesting species are dredged in deeper water or are sometimes thrown ashore during storms, and others occur in the Gulf of Mexico in shallow as well as deep water. One of these is the massive, heavily-armored, rigid Penta ceros reticularis, the species commonly sold in shell shops at the seaside resorts and the lar gest starfish of the Atlantic Coast. The Pacific Coast fauna is much richer and more varied, among the species being the gigantic Astenas giganteus, over two feet in diameter and six rayed, the 10-rayed Solaster decemradiata, the flat, granulated, bright-red Mediaster cequahs, the thick, flat, pentagonal, great-spined !Vidor ella armata, and the nearly armless and very small Asterino miniata. Consult Agassiz, 'North American Star-fishes,' Memoirs Museum of Comparative Zoology (Cambridge 1877); Slader , of the Challenger Ex pedition' (London 1889); Lankester, (*Treatise on Zoology' (Pt. III, London 1900) ; Locking ton, (Standard Natural History' (Vol. I, Bos ton 1884).