ANATINID&. 143 
digitiform foot; the siphons are more or less prolonged, united 
in their entire length or only at the base, and the united portion 
of these siphons is almost invariably covered with an extension 
of the shell-epidermis. There is also a small opening in the 
mantle below, at the base of the siphons. The gills are thin 
and in many cases (though not invariably) single. The palpi 
are usually long and narrow. 
There is scarcely any other family of Pelecypoda so important 
to the paleontologist, being represented throughout the strata 
from the oldest sedimentary deposits. The species living at the 
present time may be said to be only the remnants of the group; 
they are distributed all over the world, but they are nowhere 
very numerous, and some of them belong to the rarest yet 
known shells. Their maximum of development appears to have 
been during the Jurassic period. 
(Pandore.) 
PanporA (Solander), Bruguiére, 1792. 
Etym.—Pandora, the Grecian Eve. 
Syn.—Pandorella, Conrad. 
Distr.—24 sp. United States, Spitzbergen, Jersey, Canaries, 
India, New Zealand, Philippines, Panama; 4-110 fathoms, bur- 
rowing in sand and mud. Fossil, 14 sp, Hocene—; United 
States, Britain. P. oblonga, Sowb. (eviii, 48). P. inxquivalvis, 
Linn. (eviii, 49). 
Shell inequivalve, thin, pearly inside; valves close, attenuated 
behind; right valve flat, with a diverging ridge and cartilage- 
furrows; left valve convex, with two diverging grooves at the 
hinge; usually no ossicle; pallial line slightly sinuated. Outer 
layer of regular vertical, prismatic cells. 
Animal with mantle closed, except a small opening for the 
narrow, tongue-shaped foot ; siphons very short, united nearly 
throughout, ends diverging, fringed; palpi triangular, narrow ; 
gills plaited, one on each side, with a narrow dorsal border. 
KENNERLIA, Carp.,1864. Under this name are separated a few 
species, which still more resemble Myodora, than the true Pan- 
dore. They all have a thin hinge-ossicle, and the typical species 
have radiating ribs on the right valve. P. bicarinata, Carp. 
C@LODON, Carp., 1864. The form of the shell is similar to that 
of Pandora; each valve with two hinge-teeth directed towards 
the anterior adductor muscle, and in the left one they are connected 
by a thin lamina; no ossicle or pallial sinus. P. Ceylonica, Sowb. 
(eviii, 47). 
cLIDIOPHORA, Carp., 1864. Similar in form to the last; right 
valve rather tumid, with three hinge-teeth; the posterior one 
elongated ; left valve often with two teeth ; ossicle present, 
