68 



CONCHIFERA. 



ligament external, prominent ; pallial line slightly 

 sinuated ; muscular impressions square. Animal 

 with mantle open in front; siphons two, very 

 short, thick, fringed ; foot large, hooked. 



Cardium (Linn.). Cockle. Shell swollen ; beaks 

 nearly central, prominent, margins indented ; teeth 



C. aculeatum. C. nodosum. 



echinatum. Fig 106 ; f n. s. Norvegicum. 

 rusticum. pygrnseum. 



edule. Suecicum. 



fasciatum. 



107 



106 



TEIBE II. ASIPHONIDA. 



Hinge composed of many teeth . Arcada. 

 Hinge nearly or quite toothless. 

 Two mu scularimpressions : 



Covered with dense epidermis . Mytttida. 



Without epidermis .... Aviculada. 



One muscular impression . Ostreada. 



