114 



fine radiating striae, covered with minute granula- 

 tions, and a false epidermis. 



Lamarck considers the sinus in the lower valve to 

 be formed for the passage of a byssus, but from the 

 very singular cavity on the exterior of the valve, it 

 would rather indicate that it is the receptacle of a ten- 

 dinous ligament. 



Pedum spondyloideum. 



§LIMA. 

 OSTREA LIMA. 

 Che?n.7, tab. 6$, Jiff. 651. 



In this genus the sinus or notch has altogether disap- 

 peared, and the valves, being thickened and gaping, 

 form a lateral opening. The ears at the base of the 

 shell are small, but distinctly visible; on which ac- 

 count this genus is placed next in succession to the G. 

 Pedum, and is allied to the G. Plagiostoma and G. Pec- 

 ten; with which latter genus many authors have con- 

 founded it. Shell thin, of a very delicate, white, semi- 

 pellucid, solid substance; the valves of nearly all the 

 species flattened, some more ventricose than others, 



