CONCHOLOGY. 81 
S. longitudinalis. S. crassisquama. 
S. costatus. S. ducalis. 
S. longispinous. S. violascens. 
ee FeEGise, a S. microlepos. 
S, variegatus. S. crocens. ' 
~ S, avicularis. S. radians. 
S. zonalis. S. aurantius. 
S,. Americanus.* 
8. Genus Podopsis. Pl. IX. 
Animal. Unknown. 
Shell. Subregular, somewhat thick, equilateral, symmetrical, 
inequivalve, adhering by the extremity of the shorter valve; the 
other terminating in a pointed, reflexed, and median summit. 
Two fossil species. 
FAMILY XIX. 
OsrracEa. Six genera. 
1. Genus Ostrea. PI. IX. 
Animal. Body compressed, more or less orbicular ; edges of 
the mantle thick, not adhering or retractile, and provided with 
a double row of short and numerous tentacular filaments; two 
pairs of elongated and triangular labial appendages; a subcentral 
bipartite muscle. 
Shell. Irregular, inequivalve, inequilateral, roughly foliaceous, 
the left or inferior valve adhering, larger and deeper than the 
other, its summit prolonged with age into a sort of heel; the right 
or superior valve more or less operculiform ; hinge oral, toothless ; 
ligament subinterior, short, inserted in an oblong cardinal cavity 
increasing with the summit; muscular impression single and sub- 
central. Found in all seas near the mouths of rivers. Defrance 
enumerates one hundred and twenty species. Lamarck thirty- 
three fossil, forty-nine living. 
Ostrea edulis. Ostrea ruscuriana. 
