82 PHOLADIDiE. 



surface as far as the auricle. This latter, which is smooth, 

 small, and ear-shapetl, projects at its upper part above the 

 summit of the beak, and is internally cut off as it were from 

 the body of the shell by its lower edge, which almost 

 straight, and scarcely declining, projects like a ledge over 

 the subunibonal region. Its basal line is thus almost at 

 right angles to the hinder margin, whilst its much arcuated 

 posterior outline runs nearly parallel to the base of the 

 lateral triangle. This ear-shaped appendage is also most 

 strongly reflected outwards, and is internally rather closely 

 grooved with concentric costellaj ; its hinder termination is 

 attenuately rounded, and its front extremity is in the adult 

 concavely, in the young subrectilinearly, more or less ob- 

 liquely subtruncated. 



The entire shell is white, and faintly glossy ; there is an 

 extremely oblique lamina surmounted by a tooth-like pro- 

 cess upon the hinge margin, running at acute angles to the 

 very oblique and flat subunibonal blade, which latter is 

 clavate, and in the most perfect specimens we have met with 

 either tuberculated or jagged at its edge near its termina- 

 tion Both the posterior and anterior edges of the valves, 

 which are inclined to solidity, are rectilinear, the front 

 being nearly perpendicular, the hinder much more oblique ; 

 but in the young these sides are rather more parallel, and 

 the central, or linguiform portion of the shell, much more 

 narrow. The ventral apex is narrow, but not acute, and 

 its internal tubercle rather broad and compressed. The 

 pallets are very curious, and of a sponge-like look and 

 colour. They are remarkably large, in some measure re- 

 semble a quill In shape, are usually more or less curved, 

 and have their stalk or unbarbed portion most minutely 

 tuberculated. The upper portion, which is usually about 

 one half of the entire length, and even at its broadest part 



