118 PHOLADID.E. 



is tlie more attenuated. The hinge-margin is reflected, 

 but neither diambered, nor extending over any considerable 

 portion of the umbonal region. The solitary accessory 

 plate, which rests upon the front dorsal edges, is rather 

 large, fragile, testaceous, elongated, taj)ering off to a more 

 or less rounded point anteriorly, and posteriorly subtrun- 

 cated and bending inwards. Its sides are retuse in the 

 middle ; the surface concentrically striolated, and divided 

 lengthways by a distinct, shallow, groove-like excavation. 

 The subumbonal tooth-like apophysis is peculiarly slender, 

 flat, arcuated, rather oblique, and but little expanding at its 

 extremity. The hinge-margins are armed with an ex- 

 tremely oblique tooth-like process, attached by its entire 

 length, and only projecting above it in one valve. 



Animal elongated, white, body oblong; siphonal tube 

 very long, pale brown, minutely dotted with tawny or red ; 

 covered with closely-studded papillse (which, imder the 

 microscope, appear hollow), towards the extremity. Ori- 

 fices dusky-rayed, or longitudinally banded with purplish- 

 brown, internally ; the branchial with twelve rays or long 

 cirrhi, and intermediate smaller ones ; the anal plain. 

 Mantle in front dotted with opaque, white specks, foot ob- 

 long-lanceolate, truncate. This animal can close its shell 

 much more completely than the other British Pholades 

 but its siphon is scarcely so retractile. It is highly mus- 

 cular. Pholas candidus is very active, rapid in its motions 

 within its hole, withdrawing to its inmost recesses speedily 

 on being disturbed. 



The absence of a beak, combined with the possession of a 

 single accessorial plate, easily distinguish the shell of this 

 species from its English congeners. It never attains to any 

 considerable size, rarely exceeding two inches in length, and 

 five-sixths of au inch in breadth, and is much more usually 



