spoxdylidjE. 559 



straight, with about fifteen denticles on each side ; cartilage 

 pit triangular, the area slightly concave and longitudinally 

 striated. Muscular impression sub-central; pallial lino 

 simple. 



Ex. L. Sarsii, Loven, pi. 128, fig. 2, 2, a. 



Of this curious genus there is but one species yet de- 

 scribed, from Norway and the Mediterranean. 



Fam. SPONDYLIDiE. 



Mouth with foliaceous lips ; palps short, oblong, pointed. 

 Mantle freely open, the margins thickened, and furnished 

 with numerous rows of tentacular cirrhi, many of which are 

 truncate, and end in a smooth, convex surface ; gills large, 

 equal, separate. Foot small, cylindrical, truncated, ending 

 in a disk, from tlie depressed centre of which issues a 

 small, cylindrical tendon terminating in a small, oviform, 

 fleshy mass. 



Shell irregular, attached by the right valve, radiately 

 ribbed, spiny, or foliaceous. 



Genus SPONDYLUS, Linnaeus. 



Shell inequivalve, adherent, spiny or rough ; beaks un- 

 equal, eared ; inferior valve with an external, flat, triangular 

 cardinal area, divided by a groove, and enlarging with 

 age. Hinge with two strong teeth in each valve, with an 

 intermediate ligamental pit, communicating at its base with 

 the external groove ; ligament internal. Muscular impres- 

 sion double ; pallial line entire. 



