328 VENERID^E. 



anteriorly, but as they approach the posterior end become less 

 pronounced and are resolved into dentations : tubes short, 

 scarcely protruding beyond the shell, united, of much the 

 same size, rufous around the orifices; the upper orifice is 

 almost plain or has a few scalloped points ; the lower orifice 

 has eight short dull-rufous cirri : gills pale brown : palps 

 short and triangular, strongly striated transversely within, 

 and less so on the outward surface : foot very large, occupying 

 nearly the ventral range, and always presenting itself as axe- 

 shaped ; the heel is rather slender and bluntly pointed, but the 

 rest of the foot can sufficiently protract itself to represent a 

 thick, short, strong, broad linguiform organ ; its pure white 

 colour is relieved by beautiful vertical lines of brilliant snow- 

 white. (Clark.) 



SHELL almost circular, compressed, solid, opaque, rather 

 glossy : sculpture, numerous flattened concentric laminae which 

 are imbricated or fold backwards, and become closer and irre- 

 gular at the sides ; the surface is also covered with still more 

 numerous microscopical longitudinal striae which exhibit the 

 inner texture of the shell : colour yellowish-white, usually 

 variegated with rays or zigzag streaks of reddish-brown, 

 purplish-red, or pink of various shades, which are occasionally 

 broken and sometimes present the appearance of white rays 

 on a dark ground : epidermis thin, yellowish, only observable 

 in young specimens, as it is rubbed off in the adult by the 

 continual friction of sand : margins rounded on all sides except 

 below the beak, where the lunule is excavated ; the posterior 

 side has a blunt angle in the middle, and the anterior side 

 appears high-shouldered and also forms an obtuse angle where 

 the lunule ends: beaks separated, considerably and some- 

 what obliquely recurved : lunule heart-shaped, defined by a 

 deeply impressed line, coarsely striated in an oblique direction, 

 usually of a purplish hue ; lips prominent or pouting : corselet 

 narrow, but deep: ligament rather long, horncolour, sunk 

 within the corselet : hinge-line rounded or obtusely angled : 

 hinge-plate thick, broad, and flexuous : teeth, in the right valve 

 four cardinals, that on the anterior side being small and tuber- 

 cular, and the other three laminar and divergent (the middle 

 one cloven or double) ; in the left valve are three divergent 

 laminar cardinals, the posterior one being double; lateral 

 tooth in each valve long, and more like part of the hinge-plate : 

 inside polished and slightly freckled, sometimes stained with 

 purple on the posterior side ; margin bevelled : pallial scar 



