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Order IL MOLLUSCA. ACEPHALA^ 



Section I. BRACHIOPODA. 



Shell with two valves; lobes of the cloak free anteriorly; arms is- 

 suing from between the lobes at the margin of the mouth ; all the 

 species are marine and permafientlij attached. 



Pedunculata. 



a. Shell supported on a fleshy peduncle. 



Linffula. 



b. Peduncle passing through the apex of one valve. 



Terebratula. 



Spirifer. 



Magas. 



Sksselia. 

 Discina. 

 Criopus. 



Obscure genera, apparently free, and extinct. 

 Pentamerus. 

 Productus. 



