C. B. Davenport 



the mud-flats like the oyster, but they never lose their power of free migration. The 

 jingle shells (Anomia simplex) are permanently attached to stones or larger shells, 

 such as Pecten, from early life. On the lower beach one also finds two species of 

 Area (Area transversa and Area pexata) ; the hen-clams, Mactra solidissima and Mac- 

 tra lateralis; the hard clam, Venus mercenaria ; and Liocardium mortoni — all lying 

 on or imbedded in the muddy bottom. Here also are found certain species of lamel- 

 libranchs that burrow in the mud or sand and, to facilitate that burrowing, have 

 become elongated; namely, the soft-shelled clam, Mya arenaria; the razor clam, 

 Ensis americana, and Solenomya velum. This great group of bivalves represents then 

 a society of animals that are fairly common because of favorable food conditions, but 

 very helpless and much exposed to predaceous animals, were it not for their hard shell 

 or their habit of burrowing into the mud. 



b. The crawling species belong chiefly to the three groups of Mollusca, Echino- 

 derma, and Crustacea. The crawling molluscs are slow-moving snails (Gastropoda) 

 which are there partly to feed on decaying animal and vegetable matter, partly to feed 

 on the growing Ulva, and partly to prey upon such living animals, chiefly bivalves, as 

 have no means of escape. The chief omnivorous and carrion snail is the mud snail, 

 Nassa obsoleta (Fig 4), which is abundant everywhere and even remains exposed on 

 the middle beach at low tide, if busy feeding on a dead oyster. The little snails, 

 Anachis avara and Astyris lunata, feed on the Ulva, or sea lettuce. The carnivorous 

 species are of larger size and include two Muricidae, Eupleura caudata and Urosalpinx 

 cinerea ("oyster-drill"), and the great whelks, Fulgur caniculatum and Fulgur carica. 

 All these feed upon oysters, scallops, and other surface bivalves by drilling holes 

 through the shell. Two species of Naticidse, Neverita duplicata and Lunatia heros, 

 seek out the burrowing lamellibranchs, and so we find them burrowing into the sand. 

 Then, too, they find in the sand of the beach the proper material for their egg cases, 

 which are made out of agglutinated sand molded in the shape of a spiral collar. The 

 crawling echinoderms are chiefly the starfishes, which are here because of the oysters 

 and other bivalves upon which they prey. They cannot bore through the oyster's 

 shell, and so they smother it until it is forced to open its valves for fresh water. The 

 crawling Crustacea, finally, feed on organic debris of all sorts. Here belong the crabs, 

 such as the three spider crabs, Libinia canaliculata, Libinia emarginata, and Libinia 

 dubia, of which the latter comes farthest in-shore. Here, too, are the three mud crabs, 

 Panopeus depresus, Panopeus herbstii, and Panopeus sayi, of which three the latter 

 is found nearest the sand spit. On the very edge of the submerged zone are found 

 also the two hermit crabs; the small one, Eupagurus longicarpus, finds protection for 

 its abdomen in the cast-off shells of the small gastropods Nassa and Anachis. The 

 large species, Eupagurus pollicaris, occupies such large shells as those of Lunatia heros 

 and Fulgur carica. These scavengers, carrying their borrowed shells behind them, 

 travel quickly along, but just below, the edge of the water, seeking for dead fish and 

 other organic matter that may be resting there. Finally, the horseshoe crab, Limulus 



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