LUCINIDA. 209 
Shell massive, trigonal, ornamented with radiating ribs and 
imbricating foliations; margins deeply indented; byssal sinus 
in each valve large, close to the umbo in front; hinge teeth 1:1, 
posterior laterals 2°1. 
A pair of valves of 7. gigas, weighing upwards of 500 pounds 
and measuring about two feet across, are used as benitiers in 
the Church of St. Sulpice, Paris. (Dillwyn.) Captain Cook 
states that the animal of this species sometimes weighs twenty 
pounds, and is good eating. 
Axes of great size, weighing seven or eight pounds, are made 
from the thickest portion of the giant Tridacna by the natives 
of the Caroline Islands.—Dr. J. C. Cox. 
uipporus, Lamarck, 1799. The “ bear’s-paw clam” has close 
valves with two hinge-teeth in each. It is found on the reefs in 
the Coral Sea. The animal spinsasmall byssus. H. maculatus, 
Lam. (cxxviii, 89-90). 
EurypDEsMA, Morris, 1845. 
Distr.—E. cordata, Sowb. Devonian? N. So. Wales. 
Shell oval or roundly cordate, rather thin, but very much 
thickened near the beaks, concentrically striated or nearly 
smooth; beaks strongly incurved, with a sort of an excavated 
and gaping lunette in front; ligament large, occupying the 
greater part of the posterior, more or less straight hinge-area, 
which is broad and extends below the beaks so as to make the 
ligament almost internal, one large subconical cardinal tooth in 
the right valve somewhat curved upward and corresponding to 
a pit in the left; several small muscular impressions near the 
hinge, but no other larger ones perceptible, neither has the 
pallial impression been as yet traced out. 
( Lucinacea.) 
Famity LUCINIDA. 
Shell orbicular, free, closed; hinge-teeth 1 or 2, laterals 1—1 
or obsolete ; interior dull, obliquely furrowed ; pallial line simple ; 
muscular impressions two, elongated, rugose ; ligament external 
or subinternal. 
Animal with mantle-lobes open below, and having one or two 
siphonal orifices behind; foot elongated, cylindrical, or strap- 
shaped (ligulate), protruded at the base of the shell; gills one 
(or two) on each side, large and thick, oval; mouth and palpi 
usually minute. 
The Lucinide are distributed chiefly in the tropical and tem- 
perate seas, upon sandy and muddy bottoms, from the seashore 
to the greatest habitable depths. The shell consists of two dis- 
tinct layers. The family first appeared in the Silurian. 
