FAMILY PHOLIDiE PHOLAS. 247 



FAMILY PHOLID^. 



Shell without a tubular sheath. Hinge either luith one or more accessory bony pieces, or 

 gaping widely in front. Penetrate by boring into wood, stones, or indurated clay. 



GENUS PHOLAS. Linnceus. 



Animal with its mantle reflected on the dorsal portion, connecting together the valves and 

 accessory pieces ; anterior opening moderately small. Foot short, oblong and flattened. 

 Tubes often elongated and united into one, which is very extensible. Mouth small, with 

 very small labial appendices. Gills long, narrow, and a little unequal on each side, united 

 in the same line for almost their entire length, and prolonged into the siphon. Shell trans- 

 verse, gaping at both sides ; hinge-margin rolled outwards, and toothless : a rib-like curved 

 tooth arises from the cavity of the beaks, and is directed across the shell. 



Pholas ceispata. 



PLATE XXXn. FIG. 806. i. B. 



Pholas crispala. LiN. Syst. Nat. p. 1111. LiH. 1. c. Vol, 2, p. 518, Ed. Brux. 

 P. id. RossEL, Essei Jour. Nat. Hist. Vol. 1, p. 50. 



P. id. GoDLD, Invertebrata of Mass. p. 27. 



Description. Shell large, thick and strong, oval-oblong, rounded behind; subangular or 

 beaked in front ; both extremities widely gaping, the valves touching only at two points the 

 hinge and middle of the basal margin. Surface divided into two portions by a broad furrow, 

 running almost vertically from the beaks to the base ; the anterior portion coarsely marked 

 with lamellar concentric plates. Within smooth, but showing the outer broad vertical furrow. 



Color, soiled greyish white, occasionally rust-colored. 



Vertical axis, 1-5 - 2-0 ; transverse ditto, 2-5 - 3- 0. 



This species is common to Europe and America. On the coast of the United States, it 

 appears to range from Massachusetts to Carolina. Large single valves are occasionally found 

 on the shores of Long-island. It is more abundant on the seacoast south of New- York. 



