MYA. 247 
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 twe and a half. 
tuberculata, shell long-ovate, surface corrugated. 
undulate-tubercled, ribbed ; disks compr essed, 
base falcate ; shell thick and rugged 5; 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. 
rugosa, shell broad-ovate ; surface wrinkled tu- 
berculated, ribbed, undulated ; disks swelled ; 
base faleate : ; 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 wuscle.) shetl varying in form 
and surface, very thick and heavy 5 epidermis 
horn-colour, different shades ef 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 oue end ; often wax- 
yellow under the epidermis; reddish purple 
19 
