76 CONOHOLOGY. 



S. longispinous. S. microlepos. 



S. regius. S. crocens. 



S. variegatus. S. radians. 



S. avicularis. S. aurantius. 



S. zonalis. 



7. Genus Podopsis. 



Jlnimal. 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. 



OsTRACEA. Six genera. 



1 . Genus Ostrea. 

 Jinimal. 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 car- 

 dinal cavity increasing with the summit ; muscular impression 

 single and subcentral. Found in all seas near the mouths of 

 rivers. Defrance enumerates one-hundred and twenty species. 

 Lamarck thirty-three fossil, forty-eight living. 



Ostrea edulis. Ostrea ruscuriana. 



O. borealis. O. Canadensis. 



O. cochlear. O. mytiloides. 



O. gallina. O. trapezina. 



O. lingua. O. rufa. 



