CONTRIBUTIONS TO PALEONTOLOGY. 345 



The original specimen consists of impressions of the exterior of five 

 or six individuals, some of them quite young, the largest one measuring 

 about one inch and a quarter in diameter. No other specimens of this 

 species have been found, so far as I know. 



Geological Formation and LocaHty.— In the arenaceous shales of the 

 Hamilton group, at Hamilton, Madison county, New York. 



Cab. Nat. 44 



