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. 129./.) 



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



PLACUNA Bruy. Shell very much compressed, per- 

 laceous, with two internal lamellar, sagittate, cardinal 

 teeth in one valve, (fig. 129. b, 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. Mth. 173. f. 2. 



FAMILY 5. ETIIERID^E. River Oysters. 



Irregular, inequivalve, foliaceous ; pearly within ; epi- 

 dermis olive green ; ligament partly internal and partly 

 external. 



ETHEBIA Lam. Muscular impressions two ; shell irre- 

 gular ; teeth none. 



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



MULLEBIA De Fer. Muscular impression single ; shell 

 sub-quadrate ; hinge irregular ; teeth none. 

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



Abridged from Placunanomia Sow. 



