PSAMMOBIA. 393 



golden yellow, but afterwards horncolour, more or less annu- 

 lated, separating the valves (as in T. donacina) by an ellip- 

 tical gape : corselet short but deep : hinge-line almost straight 

 or very little curved in the adult, obtusely angular in the 

 young, occasionally stained inside with rose-colour : hinge- 

 plate narrow and thick, abruptly truncate at the outer end of 

 the ligament : teeth, in the right valve two small knob- like 

 and diverging cardinals, the anterior being a trifle the larger ; 

 in the left valve a small erect cardinal in the centre of the 

 hinge, seated in a cavity, besides another minute laminar 

 one in a line with the beak and at a right angle to the edge 

 of the hinge-plate ; the three largest teeth are bifid : inside 

 polished and very glossy, coloured and rayed like the out- 

 side, and sometimes having a short white longitudinal streak 

 below the beak, microscopically fretted throughout, and 

 indistinctly striated lengthwise towards the edge, which is 

 thickened: pdtlial scar well defined ; sinus oval, not very large 

 or deep, extending from the posterior muscular scar about 

 halfway across the interior, apparently double in consequence 

 of a shifting or enlargement of the tubular base : muscular 

 scars irregularly triangular, anterior the larger of the two. 

 L. 0-6. B. 1-15. 



Var. gracilis. Shell broader in proportion to its length, 

 flatter, and of a slighter consistency, somewhat gaping at both 

 ends ; a few of the concentric striae assuming the form of 

 irregular grooves or ridges ; colouring more delicate, some- 

 times bright orange or marked with short purplish streaks, 

 and not unfrequently milk-white with dusky or pure white 

 streaks. 



Habitat : English, Welsh, Irish, and Scotch coasts, 

 from one extremity to the other, in sand and among 

 nullipores, at depths betAveen 4 and 85 fathoms, but 

 locally distributed. The variety is from deep water off 

 Shetland, and resembles Galeomma Turtoni in shape. 

 P. tellinella is a fossil of the Coralline Crag. It inhabits 

 the upper and western coasts of- Norway, in 3-40 fa- 

 thoms ; and M' Andrew has taken it on the Lusitanian 

 coasts, in 15-30 fathoms. 



It is an active little mollusk burrowing and swimming 



s 5 



