Contributions to Invertebrate Palseontologij . 575 



than an inch in transverse diameter, while the species above referred 

 to is minute. The occurrence of forms of this genus in rocks of 

 Devonian age is also a new feature in its history ; as those of 

 Europe are conflned to the Lower Silurian formations and the 

 lower beds of the Upper Silurian ; while these occur above the 

 middle Devonian. 



Formation and Locality. — In the Cleveland shale at Sheffield 

 and Birmingham, Erie Co., Ohio. 



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