344 



POPULAR CONCHOLOGY. 



whole surface ; the upper is flatly conical, like a Patella ; 

 no hinge. 



Crania. Retz. ( Orbicula Cuvier.) — Shell compressed, 

 somewhat square, inequivalve, equilateral, the upper valve 

 convex and PafeZ/a-shaped, the lower 

 flat and attached, and not possessing a 

 hole ; the interior exhibits four very 

 distinct muscular impressions ; no car- 

 dinal processes, and no hinge. Animal, 

 with two large, horizontal, cirrhated, buccal appendages, 

 each forming a short spiral arm curved inwards, free and 

 unprovided with any skeleton.* — 4 species; also fossil. 



Found in the Indian Seas, and on the coasts of Scot- 

 land and Ireland. Forbes says, " the arms are extended 

 horizontally, each forming a rather short, graceful, plume- 

 like curve, the fringe side being outermost. The fringes 

 are long and rather stiff, and can be extended slightly 

 beyond the shell ; they are of a fleshy white colour. 

 When the upper valve is removed, the fringed arms are 

 seen lodged in it." 



Dr. Mantell mentions that the fossil specimens of this 

 genus are often found adhering to the Echinites of the 

 chalk, and that in many of the quarries in Kent and 

 Sussex the helmet Echinites bear groups of these shells. 



Family 5.— D1SCIN1DJE. 



The mouth arms are fleshy ; at the base there is no cal- 

 careous or other support : the under valve is without pro- 

 cesses, but has a slit for the exit of a short sinewy 

 tendon ; the upper valve is cone-shaped, or bowl-shaped ; 



* Forbes' British Moll. 



