INVERTEBRATE ANIMALS OF VINEYARD SOUND, ETC. 359 



depth beneath the surface of the sand, merely projecting the tubes up- 

 ward to the surface. It is, nevertheless, like other bivalves, often rooted 

 out of its burrows and devoured by many fishes, especially, in this re- 

 gion, by the " scup" and flounders. This species is found all along the 

 coast, from the Gulf of Saint Lawrence to South Carolina. 



The Macoma fusca (Plate XXX, fig. 222) is a related species, also 

 furnished with similar, very long, slender, separate tubes, and is, therefore, 

 able to live deeply buried beneath the surface. This species is much more 

 abundant than the preceding, between tides, but it most abounds on 

 shores that are more or less muddy, and in estuaries. But when living on 

 the sandy shores, and where the water is pure, it becomes much smoother 

 and more delicate, and is often of a beautiful pink-color and much 

 larger than the specimen figured. When living in the muddy estuaries 

 it generally has a rough or eroded surface, more or less irregular form, 

 and a dull white or muddy color, often stained with black, resembling 

 in color the Mya arenaria, with which it is sometimes associated. It is 

 dug up and eaten by the tautog and other fishes. 



The pretty little Tottenia gemma (Plate XXX, fig. 220) is a species 

 peculiar to sandy shores, both above and below low- water mark ; and 

 it often occurs in immense numbers on the sandy fiats laid bare by the 

 tides, buried just beneath the surface of the sand. Owing to its small 

 size it is, however, liable to be overlooked, unless particularly sought 

 for. It is an active species and burrows quickly. It is peculiar in be- 

 ing viviparous, as was first observed by Mr. G. H. Perkins, who found, 

 in January, from thirty to thirty-six, well-formed young shells^ of nearly 

 uniform size, in each of the old ones. This shell has a lustrous, con- 

 centrically grooved surface ; the color is yellowish white or rosy, with 

 the beaks and posterior end usually purple or amethyst-color. It occurs 

 all along the coast from Labrador to South Carolina. The common 

 u round clam" or " quahog-clam," Venus mercenaria, (Plate XXYI, fig. 

 184, animal,) is also common on sandy shores, living chiefly on the 

 sandy and muddy flats, just beyond low-water mark, but is often found 

 on the portion laid bare at low-water of spring-tides. It also inhabits 

 the estuaries, where it most abounds. It burrows a short distance be- 

 low the surface, but is often found crawling at the surface, with the shell 

 partly exposed. It has short siphon-tubes, united from the base to 

 near the ends, and a large, muscular foot, with a broad, thin edge, by 

 means of which it can easily burrow beneath the sand when necessary. 

 The lobes of the mantle are separate all around the front and ventral 

 edge of the shell, and their edges are thin, white, and folded into deli- 

 cate frills, some of which, near the siphon-tubes, are elongated and 

 more prominent. Owing to the broad opening in the mantle, the foot 

 can be protruded from any part of the ventral side, and has an ex- 

 tensive sweep, forward and backward. The foot and mantle edges 

 are white ; the tubes are yellowish or brownish orange toward the end, 



