SQO SHELLS AND SHELL-FISH. PART II. 



passes through an opening near the umbo of the 

 lower or smaller valve, which is flat; the other is 

 convex. (fig.Ug.f.) 



A. Ephippium. Sow. Man. f. 186. 



Placuna Brug. Shell very much compressed^ per- 

 laceous^ with two internal lamellar, sagittate, cardinal 

 teeth in one valve, {fig. 129- h, c.) 



Placunomia.* Shell attached, with the form and gene- 

 ral structure of Anomia, but with two sagittate car- 

 dinal teeth. 



Cumingii. Sow. Man. f. 189. 



Placuna Brug. Shell not attached, foliaceous, roundish ; 

 the valves equally flattened : united to Pecten by 

 Pleuronecta. 



P. placenta. En. M^th. 173. f. 2. 



Family 5. ETHERID.iE. River Oysters. 



Irregular, inequivalve, foliaceous ; pearly within ; epi- 

 dermis olive green ; ligament partly internal and partly 

 external. 



Etheria Lam. Muscular impressions two ; shell irre- 

 gular ; teeth none. 



E. semilunata. Sow. Man. f. 155. 



MuLLERiA De Per. Muscular impression single ; shell 

 sub-quadrate ; hinge irregular ; teeth none. 

 M. lobata. Sow. Man. f. 192. 



Abridged from Placunanomia Sow. 



