CARDIUM. 269 



ance of being partially decussated ; the ribs are also striated 

 transversely, but less distinctly than the furrows ; the whole 

 surface is covered with frost-like microscopical markings : colour 

 yellowish with a reddish tinge : epidermis fibrous, only obser- 

 vable near the margins, having been removed in other parts 

 by continual attrition : margins rounded on the anterior side, 

 and sloping with an oblique curve in front to the posterior side, 

 which is produced, much broader than the other side, truncate, 

 and exhibits a long and narrow but distinct gape extending from 

 the edge of the hinge-line to the angle where it joins the ventral 

 margin : beaks almost touching each other ; umbones tumid : 

 Ugament cylindrical and thick, resembling the chrysalis of a large 

 fly, prominent, reddish-brown: hinge-line obtusely angular: 

 hinge-plate folded back towards the beaks, occupying scarcely 

 one-third of the circumference : teeth, in the right valve two 

 erect cardinals, besides two laterals on the anterior and one on 

 the posterior side ; in the left valve two similar cardinals, the 

 posterior of which is very much smaller than the other, besides 

 one lateral on each side ; all the lateral teeth are triangular 

 and pointed : inside rather glossy, fluted towards the front and 

 anterior margins, the concavities corresponding with the outside 

 ribs ; the under side of the furrows is flat: pallial scar broad 

 and entire: muscular scars about equal in breadth, but the 

 anterior one is the longer. L. 32. B. 3 - 35. 



Habitat : Not uncommon on the South-Devon 

 coasts, especially at Paignton near Torbay, but scarcely 

 ever found in a living state ; Weymouth (Thompson) ; 

 Guernsey (Lukis) ; Dublin Bay (Brown) ; Point of 

 Ayre, Isle of Man (E. Forbes) ; Hebrides and Orkneys 

 (Pennant). These last two localities, as well as the 

 next, are very doubtful. Mr. James Smith says, on the 

 authority of the late Dr. Landsborough, that it occurs 

 in the glacial deposit at Stevenston. Sars has dredged 

 a fine specimen near Bergen ; De Gerville, Collard des 

 Cherres, and Mace have recorded the species as in- 

 habiting the North of France ; and many other authors 

 have described or enumerated it as Mediterranean. It 

 may on the whole be considered a southern form. 



Young specimens are globular and not angular ; and 



