[359] INVERTEBRATE ANIMALS OF VINEYARD SOUND, ETC. 65 
depth beneath the surface of the sand, merely projecting the tubes up- 
ward to the surface. Itis, 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 flats 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. Tbe common 
“round clam” or ‘‘ quabog-clam,” Venus mercenaria, (Plate X XVI, 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 ic 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, 
