ACEPHALA OR LAMELLIHUANCHIATA. 



427 



(from the Gr. monos, one, and mus, muscle), or those whose 

 shell is closed by one muscle, as the Oyster, etc. 



FIG. 645. 

 FIG. 643. FIG. 644. 



Spha'riuni partumeium, 

 Say. Northern States. 



Astarte castanea, Say. 

 Casco Bay and southward. 



FIG. 646. 



Sphterium rliombnideum, Say. 

 Northern States. 



Cardium islandicum, linn. 

 North Atlantic. 



FIG. 647. 



Thyasira Gavldii, Stim. 

 Coast of New England. 



FIG. 648. 



VHLU Sitvpai'diauus, Lea. Southern States. 



FIG. 650. 



FIG. 649. 



Unio spinosa, Lea. Reduced. 

 Georgia. 



Unio flexuosus, Raf. Reduced. 

 Western States. 



