GENUS XXXII. PATELLA. 139 



Orbicula. Shell orbicular, flat, fixed, composed of two valves, 

 the lowest valve very thin and adhering to other bodies ; 

 the hinge unknown ; the animal furnished with two long 

 arms, like Anomia Terebratula (see Patella anomala, 

 Mul. Zool. Dan. p. 14. t. 5. Prod. 3870). 



Perhaps we may place here Lamarck's genus Radiolites, as 



follows : 



Radiolites. Shell irregular, inequivalve, striate on the out- 

 side ; the lower valve turbinated, the upper convex or conic ; 

 neither hinge nor cartilage (see Park. Organ. Rem. vol.3, 

 p. 206. t. 16. f. 1). 



