MYA. 



epidermis horn- colour ; surface irregularly cor* 

 rugated and tubercled ; tubercles largest near 

 the center of the disk, and often eroded ; car- 

 dinal teeth furrowed and crenulated ; lateral 

 teeth short, thick, crenate. Dimensions three 

 inches by two and a half. 



tuberculata, shell long-ovate, surface corrugated^ 

 undulate-tubercied, ribbed ; disks compressed^, 

 base falcate ; shell thick and rugged ; beaks 

 flat near the posterior end ; hinge-margin strait- 

 ish ; epidermis dark brown or horn-colour ; 

 elongated tubercles are thickly scattered over 

 the surface ; cardinal teeth crenated, lateral 

 ones long and striated ; pearly white, with ir- 

 regular greenish spots within. Dimensions 

 about four inches by two and a fourth. 



mgosdi shell broad-ovate ; surface wrinkled tu- 

 berculated, ribbed, undulated ; disks swelled ; 

 base falcate ; shell compressed and thin before ; 

 beaks slightly elevated ; hinge-margin com- 

 pressed, keeled ; epidermis dark brown, pearly 

 white under it ; surface rough and scaly, wrink- 

 led transversely and undulated lengthwise. 

 Dimensions two inches and a quarter by three. 



crassa, (thick-shell muscle,) shell varying in form 

 and surface, very thick and heavy ; epidermis 

 liorn-colour, different shades of brown and 

 black ; beaks carious, often much eroded, pure 

 pearly or silvery white. Dimensions some- 

 times four and a half inches by three. 



purpurea, (purple muscle,) shell suboval, and 

 somewhat compressed ; smaller wrinkles be- 

 tween larger ; colour dark- brown ; beaks cari- 

 ous, not prominent, near to one end ; often wax- 

 yellow under the epidermis ; reddish purple 

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