MARINE MOLLUSCA OP THE UNITED STATES. 187 



mis thick, dark violaceous, blackish, or chestnut-brown; within 

 pearly. 



Length 4.5-6, height 2.5-3 inches. 



Animal dark-orange or reddish ; edible. 



Northern Coast, northwards. {Eur.) 



2. M. plicatula, Lamarck. Fig. 512. 



Anim. s. Vert., vii. 22. 1822. 

 M. semicostata, Cour., Journ. Pliila. Acad., vii. 244, t. 20, f. 7. 



Shell oblong, obliquely dilated, somewhat falciform ; surface 

 with approximated deep furrows radiating towards the dilated 

 margin, fainter on the basal margin, but more distinct near the 

 beaks, which are often eroded ; a few distant, concentric, narrow, 

 impressed lines cross the radiating stria?; beaks prominent, 

 rounded; hinge margin straight, ascending; basal margin concave, 

 depressed, with a small fissure for the byssus. Epidermis greenish- 

 yellow to reddish-brown ; within pearly, occasionally purple- 

 tinted. 



Length 2.5-4.5, height .8-1.5 inches. 



Whole Coast. 



Inhabits salt marshes, estuaries, and brackish waters. 



3. M. tulipa, Linnaaus. Fig. 514. 



Modiola Americana, Leach., Zool. Misc., ii. t. 72, f. 1. 1815. 

 Modiola castanea, Say, Journ. Philad. Acad., ii. 266.% 1822. 



Shell oblong, rather thin, vcntricose; hinge margin elevated in 

 a right line from the beak to the alated angle, from which it de- 

 clines in a right line to nearly an equal distance, the alar angle 

 rounded ; anterior margin short and small ; basal margin slightly 

 contracted in the middle. Epidermis marked only by growth 

 lines, yellowish or brownish, with dark rays over the middle pos- 

 terior portion, sometimes uniform chestnut-color. 



Southern Coast. ( W. Ind. ) 



31. castanea appears in some catalogues as a distinct species, 

 but an author's specimen in Mus. Philad,. Acad, proves its 

 identity with tulipa. 



4. M. carolinensis, Conrad. Fig. 513. 



Jouru. Philad. Acad., vii. 244, t. 20, f. 6. 1837. 

 Shell dilated in the middle; disks with very numerous radiating 

 striae ; lower margin rounded and beautifully crenulate. Color 

 greenish-yellow ; within yellowish, spotted with purple. 



Charleston, 8. C. 



