248 NEW-YORK FAUNA MOLLUSCA. 



Pholas TRUNCATA. 



plate xxxiv. fig. 223. a. b. 



(STATE COLLECTION.) 



Pholas tru7tcala. Say, Jour. Ac. Nat. Sciences. Vol. 2, p. 321. 



P. id. Wheatley, Catalogue of Shells United States, p. 4. 



Description. Shell subpentangular ; anterior obtusely rostrated, wedge-shaped in the middle; 

 posterior margin broadly truncated at the tip. Valves transversely wrinkled, crossed by 

 striffi, muricated (particularly on the anterior side) with small erect scales which are not 

 arched beneath ; posterior margin without striee, and mutic. Hinge-callus without cells : a 

 small tooth on the inner margin, projecting backwards ; the dentiform process curved, promi- 

 nent, flat, slender. 



Vertical axis, ' 7 ; transverse ditto, 1 • 7. 



This appears to be a common shell on the southern coast, but is rare with us. It has been 

 found imbedded in peat bogs at Sachem's head (Connecticut), at Throg's neck (Westchester 

 county), at Glasshouse point above the city, and at Staten island, (Richmond county). 



{EXTRA-LIMITAL.) 



P. costata, Lin. (Deshayes, Conch, pi. 3, fig. 10. Gould, I. c. p. 27.) Shell very large, thin, 

 inflated, with strong crenulate radiating ribs about half an inch apart on the basal margin, becom- 

 ing abruptly closer, armed with small vaulted scales formed by transverse striae passing over them. 

 Color, white. Vertical axis, 2 '0; transverse, 7*0. Common on the shores of the Southern 

 States. An extensive bed of dead shells has been found at New-Bedford, Mass. 



P. cunciformis. (Say, Ac. Sc. Vol. 2, p. 322.) Wedge-shaped; anterior margin nearly closed, 

 transverselj' truncated from the hinge ; posterior margin with a rounded lip ; a deep furrow from 

 the beak to the middle of the basal margin, impressed within. Surface with transverse undulating 

 striffi, with elevated minutely crenate lines. Hinge-callus forming a cavity before, and without 

 cells; dentiform process filiform, incurved; hinge-plate ovate-triangular, with a short projecting 

 angle on the anterior middle, and subacute behind. Color, white. Vertical axis, 0-45; transverse, 

 0*8. Occurring frequently in old wood. Southern Coast. 



P. oblongata. (Say, lb. Vol. 2, p. 320.) Shell thin, transversely much elongated: basal and hinge 

 margins nearly parallel ; ends rounded. Valves transversely and longitudinally striated ; the striae 

 muricate, and elevated into costae on the anterior side, which are more prominently and densely 

 muricated. Hinge-callus minutely striated trans\-ersely and longitudinally, and with about twelve 

 cells, anterior to which is a recurved margin of the shell, forming a cavity; dentiform process 

 dilated, incurved, spoon-shaped, emarginate behind, and irregularly truncate at the tip. Vertical 

 axis, 1*2; transverse, 4 • 4. Carolina, Georgia, and East-Florida. 



