76 PHOLADID^. 



dorsal margin, and is never seemingly truncated in front by 

 any abrupt ascension of the dorsal margin. Its anterior 

 limit is most distinctly indicated internally by a broad and 

 appressed rim, which overlaps the edge of the body or me- 

 dial portion of the valves. This latter is never greatly elon- 

 gated, the breadth and length of the valves being frequently 

 equal to each other. 



The subumbonal blade, or tooth-like apophysis, is thin, 

 broad, arched, and nearly of equal breadth throughout, 

 neither being clavate nor much attenuated at its termina- 

 tion, nor jagged along its edge, which runs nearly parallel 

 to the lower front, and presents its sharp and not its broader 

 surface to the inner disc. The cardinal denticle and lunate 

 rim, and likewise the ventral tubercle, do not appear to 

 difter much from those of Norvagica. The pallets, or caudal 

 appendages, are each composed of a thick, suboval, shelly 

 plate, bifurcated at its extremity, and seated upon a slender 

 and more or less short, flexuous, cylindrical stalk. This 

 plate is flat upon one side, and convex upon the other, but 

 devoid of any central rib. 



The tube or sheath is long, flexuous, tapering, and devoid 

 of internal concameration ; it is usually rather solid. 



We are not aware that this has hitherto been pubHshed 

 as British, although individuals may exist in some of the 

 less noted collections, mixed up with those of Norvagica. 

 The only locality we know, is in the piles of the pier at 

 Heme Bay, from whence Mr. Hanley took them, along 

 with their animals, about four years ago. The tubes 

 were about eight inches long, and about one-sixth of an 

 inch in diameter at their broader extremity. The valves 

 did not (even those which wore the appearance of age) very 

 much exceed a quarter of an inch, which latter measure- 

 ment was the full length of the caudal appendages. 



