PLACUNA. 



Sella of Liftne, or Saddle oyster, and the Anomia Pla^ 

 centa, or Chinese Window Shell, are the best known and 

 most easily distinguished. We have never seen any 

 fossil species, but Lamarck describes one found near Metz^ 

 and figured in the Enci/cl. Method, t. 175, f. 1 — 4, from a 

 specimen of this in our possession we judge it rather to be 

 a Plicatula, 



Fig. 1. Outside of the lower valve of PL Placenta. 

 2. Inside of upper valve of the same. 



