CONCHOLOGY. 63 



A. pisolina. A. lactca. 



A. callifera. A. cancellaria. 



A. bisulcata. A. irudina. 



A. senilis. A. rhombsa. 



A. auriculata. A. corbicula. 



A. Cayennensis. A. InJica. 



A. antiquata. A. granosa. 



A. Braziliana. A. squamosa. 

 A. pistachia. 



A. ponderosa.* A. incongrua.* 



A. pexata.* A. transversa.* 



2. Genus Cucnllxa. PL VIII. 



Animal. As above. 



Shell. Trapeziforra, inequilateral, equivalve, heart-shaped ; 

 beaks far apart, separated by the angular groove of the ligament, 

 which is altogether external ; hinge hnear, straight, with small 

 transverse teeth, having at its extremity from two to five parallel 

 ribs ; valves minutely striated longitudinally ; margins crenulated. 

 The Cucullsea is distinguished from the Area by the muscular 

 impression, to one side of which is an auriform testaceous appen- 

 dage ; the shell also is more trapeziform. Inhabits the Indian 

 ocean. One living species. One fossil. 



Cucullsea auriculifera. 



3. Genus PecUincuhis, PI. VIII. 

 Animal. Body round, more or less compressed ; mantle with- 

 out cirri or tubes ; foot securiform, cleft at its inferior anterior 

 edge ; buccal appendages linear. 



Shell. Orbicular, equivalve, subequilateral ; summit nearly 

 vertical, and more or less distant ; hinge formed upon each valve, 

 of a numerous series of small teeth disposed in a curved line, 

 sometimes interrupted beneath the summit ; ligament as in Area, 

 but usually much narrower. Inhabits the British and Mediterra- 

 nean seas. Twenty-two living species. Nine fossil. 



Pectunculus pilosus. Pectunculus Pennaceus. 



P. marmoratus. P. castaneus. 



