CLASS IX. ORDER III, : 4415 
bent lips ; hinge with three teeth, all of them ap- 
‘proximate, the lateral ones divergent at the tip. 
SroNDYLUs, (thorney oyster,) animal a tethys ; 
shell hard, solid, with unequal valves ; one con- 
vex, the other ahr fiat ; hinge with two recurv- 
ed teeth separated by a small hollow. 
Cuama, (basin conk,) animal a tethys ; shell 
bivalve, rather coarse ; hinge with a callose gib- 
bosity, obliquely inserted in an oblique hollow ; 
anterior slope closed. : 
Arca, (nvah’s ark,) animala tethys ? shell bi- 
valve, equivalve; hinge with numerous sharp 
teeth alternately inserted between each other. 
Osrrea, (oyster, scallop,) animal, a tethys ; 
shell bivalve, pencrally, with unequal valves and 
slightly eared ; hinge without teeth, but furnished 
with an ovate ‘hollow, and mostly lateral, trans- 
verse groove. 
Anomia, (thin-shell,) animal siugeslndtes cili- 
ate, strap-ferm, with bristles or fringe affixed to 
upper valve; shell bivalve, one valve flatish, the 
other gibbose at the base, with a produced beak 
generally curved over the hinge ; hinge without 
teeth, but a lateral tooth within, on the margin of 
the flat valve ; two bony rays for the base of the 
animal, 
Myvrixvus, (mother pearl, muscle,) animal al- 
lied to an ascidia; shell bivalve, rough, generally 
afiixed by a byssus or beard, of silky filaments ; 
hinge mostly without teeth, with sometimes a su- 
bulate excavated longitudinal} line. 
Pinna, (wing- clam,) animal a limax; shell 
sub-bivalve, fragile, upright, gaping at one end, 
and furnished with a bissus or beard; hinge with- 
