294 The American Naturalist. [April, 



The Camerata are distinguished by the large number of supplemen- 

 tary pieces which bring the proximal arm plates into the calyx, thus 

 enlarging the visceral cavity ; all plates are heavy and immovable ; 

 the mouth and food grooves are tightly closed. 



The Articulata have to some extent the incorporation of the lower 

 arm plates with the calyx, but the plates are movable instead of rigid. 

 The mouth and food grooves are open. The infrabasals are fused with 

 the top stem joint which is not the youngest plate of the stalk. Ac- 

 cording to whether or not pinnules are present two suborders are 

 recognized : the Pinnata and Impinuata. 



An analytical synopsis of the families of Camerata as proposed by 

 the authors and as now understood is as follows : 



rhrachi'ij.-i 4ighthj npr^utnl i 



Regarding the terminology employed, special attention should be 



call-; 





3 given of the \ 



they ] 



