THE - CONCHOLOGISTS’ - EXCHANGE. 
47 
to fifty fathoms or more,” (Verrill.) It is not 
uncommon in Long Island Sound, but I have 
not yet observed it in Rhode Island. 
The other two genera of the Saxicavidze 
family are Panopzea, with eleven species, and 
Cyrtodaria with two. Panopzea Norvegica, 
Spengler, and Cyrtodaria siliqua, Chem., both 
large, rough and coarse shells, inhabit New 
England to the banks of Newfoundland, but is 
not found south of Cape Cod. 
FAMILY MY ACID. 
Shell transverse, gaping at both ends; left 
valve with a single, broad, erect tooth, received 
into a pit in the opposite valve. Animal with 
the mantle almost entirely closed; siphons 
united, partly or wholly retractile. | A small 
family composed of three genera; Tugonia, 
with six species, all inhabiting the West Coast 
of Africa; Platyodon, with one species, inhab- 
iting California, and Mya, with three species. 
Genus Mya, Linné, 1740. 
Although the genus consists of but three 
species, the individuals composing ove of these 
species are the most numerous and_ prolific 
of all known shells. This species, inhabiting 
the whole of Northern Europe, Asia and Amer- 
ica, 1S 
149. — Mya arenaria, Linné, 1767. 
Syns: 
Mya mercenaria, Say, 1822. ~Mya acuta 
Say, 1822. , 
Shell ovate, equivalve, gaping at both ex- 
tremities ; surface chalky white, covered by a 
thin, rusty brown, wrinkled epidermis; beaks 
small, pointed curved forwards; an erect 
tooth in the left valve fits into a deep excavation 
in the right valve directly under the beaks, 
Length, five inches; height, three inches; 
breadth, two inches. This species is called the 
Gaper, Old Maid and Clam, ‘In Greenland 
they form the principal food of the Walrus, the 
Arctic Fox and various birds. A Clam Bake 
is one of the peculiar institutions of Rhode 
Island. Whether clams are more abundant, 
or of better quality in Rhode Island than else- 
where, I cannot say, but they do not seem to 
be used as an article of food to any great extent 
outside of our little State. Hundreds of bushels 
are baked and consumed daily during the Sum- 
mer at our shore resorts, and there are several 
places in Providence where they may be ob- 
tained, boiled, fried or steamed, every day in the 
year. Notwithstanding the immense run on 
their banks, the supply is never exhausted, and 
no perceptible dimunition in their number is 
observed. Although the specific name, arenaria, 
means ‘‘of or pertaining to sand,” they are. 
found just as plentifully in mud or among stones 
as in sandy places. They inhabit from half 
tide to forty fathoms in depth, about a foot 
below the surface; the animals are provided 
with a very extensile tube, which extends to 
the surface through which they obtain their 
food, as explained under the description of 
Class Pelecypoda, on page 18, Vol. II. 
John Winthrop, in Journal of the Royal So- 
ciety, 1634, says, ‘“ These clams feed only on 
sand,” but their real business in life is, to purify 
our waters, by absorbing all manner of organic 
or inorganic matters, which would otherwise, 
by its accumulation, poison the air, destroy our 
fish, and render existence intolerable in the 
vicinity of our beautiful shore resorts.”’ 
The term clam is applied to this species only 
in New England. The Indian name was 
sickishuog. The Chinese call it Tsega. In 
New York and farther south a clam means 
what we call a quahog, Venus mercenaria, but 
the original owner of this name is a ponderous 
biva ve of the Pacific Coral Lagoons, Tridacna 
gigas, a small valve. of which may be seen 
hanging over the door of an oyster saloon on 
College St., in Providence, I have seen a pair 
of valves of this species measuring two feet 
across, and weighing about five hundred pounds, 
used for a holy water font, in the Church of 
St. Sulpice, in Paris. 
Another species, Mya truncata, much re- 
sembling our clam, excepting that the posterior 
end of the shell appears as if chopped off or 
truncated, is common from Cape Cod, north- 
wards to the Arctic seas, but is not found south 
of the Cape. 
To be Continua. 
