SECTION Xr. 233 



Part I. Shells that have unequal valves 

 and fluit clofe ; as the Efcallops, Oyfters, 

 Anomii^, &c. 



Part 2. Shells that have equal valves and 

 fhut clofe ; as the Cockles, Tellens, 

 Mufcles, &c. and 



Part 3. Shells with valves that never 

 fliut clofe, but are always open or gaping 

 in fome part ; as the Tridacuce, Bafon 

 Conques, or Bears Paws, the Cham^, Pin- 

 1}^, and Solenes, &c. 



Under thefe three arrangements all the 

 Bivalves yet known may be ranked. 



Thefe three arrangements are general 

 ones ; but, as I have already obferved, th^ 

 chief or eflential charafter of Bivalves is 

 their cardo, or hinge : it is that charac- 

 ter I hold as the principal one of the fyf- 

 tem, and therefore by that character alone 

 I (hall rank the families. 



But, 



