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POTERIOCRINIDiE.— POTERIOCRINUS. 



2. Family. POTERIOCRINID^. 



This family contains several genera, among which are the Poleriocrinus and Synbalho- 

 crinus. 



The plates surrounding the digestive organs of all the PoleriocrinidcB are more or less 

 tumid, and adhere to each other by broad surfaces of attachment. In some species the 

 calcareous skeleton is prolonged internally so as to materially reduce the size of the 

 internal cavity. 



As we shortly intend to propose a more comprehensive arrangement of the Crinoidea 

 than the one previously adopted, the exact limits of this family will be more particularly 

 defined in a future page. 



Genus 1. POTERIOCRINUS. (Miller.) 



Etijm. noTiiPlON. (Potherion) a drinking cup, from the supposed resemblance the 

 armless bodv bears to a common conical wine glass. All the known species of Poterio- 

 crimts occur only in the mountain limestone formation. 



Definition.— Dorso-ccntral plate tripartite ? 1; first series of perisomic plates, five, (2;) 

 second series, five (-3;) third series or ray -bearing plates, five, (4,) with two or three 

 intermediate plates, a, h, c, 



