-Asiphonophor a . 
5Y0 Asiphonophoka. MOLLUSCA. 
which tits into a pit in the surface of the other. The 
family, as now restricted, is not numerous in speciesj 
about a dozen only having been described. The genera 
are Mya*Sph(Bnia, and Tugonia. 
Genus Mya. — This genus contains several species of 
some utility. 
MYA AKENARIA (Plate 10, fig. 12), is used, both 
in this country and in North America, as food for man 
and as bait for fishes. On the banks of Newfoundland 
the fishers bait their lines very successfully with it, and 
it is said to be peculiarly acceptable to the cod. Dr. 
Gould, in his account of the Invertebrata of Massachu- 
setts, says, “ The Clam {Mtja arenaria) is still more 
important in an economical point of view than the 
oyster. It is extremely prolific; and its exhaustless 
banks are every day accessible during twelve of the 
twenty-four hours.” It is used for food, as well as for 
bait. About five thousand bushels of clams are annually 
brought to market. Immense numbers are salted for 
the bank fisheries — not less than five thousand barrels 
every year. “ Seven bushels of clams make about one 
barrel of bait ; so that thirty or forty thousand bushels 
are used in this prepared state, and perhaps as many 
more are used from the shell. The value of the clam- 
bait is six or seven dollars per barrel.” — Gould, and 
Johnston. 
MYA TRTJNCATA is boiled and eaten by the in- 
habitants of Zetland, where it is known by the name 
of “ Smurslin.” In Greenland, according to 0. Fabri- 
cius, these shells are much sought after by the walrus, 
the arctic fox, and various Northern birds. 
Passing by the families of Corbulas {Corhulidc^ and 
Pandoras {Pandoridee), we come to the second sub- 
class 
Sub- CLASS IL— A SIPHON OPHOEA. 
This sub-class is divided into three orders : — 
1. Lasiacea, in which the mantle lobes are united, 
with an anal sipbonal aperture under the hinder 
adductor muscle, and a large opening for the passage 
of the foot. 
2. Unionacea, in which the mantle lobes are free, 
slightly united behind, forming a separate and sipbonal 
opening placed under the hinder adductor muscle. 
3. Pectinacea, in which the mantles are free all 
round, without any separate opening for the vent and 
out-going current. 
Order I.— LASIACEA. 
Family— SOLFNOMYID^. 
In this family the shell is elongated, cylindrical, 
obtuse at the extremities, and gaping. The valves are 
clothed with a dark, horny, shining epidermis, which 
extends beyond the margins. The hinge has a cardinal 
tooth in each valve, and a callosity running between 
them. The family consists of only one genus. 
Genus Solenomya. — This genus contains only four 
known species. They are usually found burrowing 
in mud, in about two fathoms water, but at the same 
time are capable of leaping and swimming about with 
great freedom. Mr. Stimpson, an American concholo- 
gist, has observed them making surprising leaps and 
swimming about in the water for a considerable space 
of time without touching the bottom. The leap appears 
to be performed by the animal suddenly drawing in its 
large umbrella-shaped foot, at the same time that water 
is expelled from the hinder opening by the closing 
of the valves. The genus is represented in Plate 11, 
fig. 13, by Solenomya mediterranea. 
The families Laseidoe and Montacutidee possess 
no great interest; we will therefore pass on to the 
second order : — 
Order II.— UNIONACEA. 
Family— LUCINID^-. 
The shells of this family are of a more or less orbi- 
cular shape, free, and closed. The hinge varies very 
much ; in most cases, however, there are one or two 
cardinal teeth, and two lateral teeth in each valve, 
though these are sometimes obsolete. Externally they 
are variously sculptured, and internally they are always 
dull and obliquely furrowed. The ligament is external 
or subinternal. The species are rather numerous ; they 
are chiefly natives of temperate and tropical seas, living 
upon sandy and muddy bottoms, and ranging from the 
sea shore to great depths. A good many genera have 
been formed, their characters being derived from the 
structure of the hinge, the ligament, &c. These are 
Lucina, Loripes, Corhis, and Ungulina. The family 
is very well represented in Plate 11, fig. 14, by Corhis 
fimhriata. 
Family— ASTARTIDAl. 
In this family the shells are free, of a solid substance, 
oblong or cordate in shape, smooth or concentrically 
ribbed on the external surface and covered with a thick 
brown epidermis. The hinge is furnished with strong 
teeth — two diverging cardinal teeth in one valve, and 
one in the other. The ligament is external. Upwards 
of fourteen species have been described ; they are found 
living in sandj' mud, and are almost all found in the 
Northern seas — ranging geographically from Welling- 
