MOLLUSKS 127 
and muscular and its end flattened to serve as a pushing organ. 
The clam burrows only a short distance beneath the sand and ocea- 
sionally comes to the surface where it literally skips along by means 
of its powerful foot, aided by the flapping motion of its valves. In 
common with all other clams it feeds upon minute organisms both 
vegetable and animal. 
The Swimming Clam, (Solenomya velum, Fig. SG), ranges from 
North Carolina to Nova Scotia, where it burrows into sandy or 
muddy beaches immediately be- 
low tide level. In common with 
the razor clam, and _ sand-bar 
clam, it prefers pure ocean water. 
Ee 3 
It is not over three-quarters of 
an inch in length, and the shell 
is thin and flexible with a rich 
brown surface varied by yellow 
lines radiating from the hinge. Fig. 86; SWIMMING CLAM. Cape 
The foot of this clam can be ex- eons 
panded into an umbrella shape at its apex. When the foot is 
expanded and driven suddenly outward, the clam swims backward, 
but when the foot is suddenly withdrawn it swims forward. In 
this manner the clam is enabled to swim for 
a considerable distance through the water with- 
out touching the bottom. 
The Bloody Clam, (Argina pexata, Fig. 
87), is common under stones or within gravelly 
beaches, below low-tide level, from Florida to 
Cape Cod. It attaches itself to stones by 
means of a byssus thread which is secreted by 
' a gland in the foot. The shell is oblong, about 
Fig. 87; BLOODY — one and one-quarter inches wide, and covered 
CLAM. 

with a rough, brown skin. There are about 52 
ridges that radiate outward from the beak of the shell. The gills 
and circulatory fluid of the clam are red. Hence the popular name 
of ‘bloody clam.” 
The Ship-Worm, or Teredo, (Fig. SS), is not a worm but is 
closely related to the clams. Its peculiar elongate form and worm- 
like appearance are due to its habit of burrowing into any sort 
