GASTEROPODA. 35 



greater than the width exposed ; body-volution moderately ventricose and 

 rounded above ; the periphery a little contracted vertically, and the lower 

 side rounded and expanded more abruptly towards the aperture, gently 

 depressed towards the centre, which is partially umbilicate. Aperture 

 nearly circular. 

 Surface marked by strong revolving striae, which are crossed by fine and less 

 conspicuous concentric striae, giving sometimes a denticulate character at 

 the crossing of the two series. Shell of moderate thickness. Suture 

 neatly defined, not canaliculate. 



This species is less distinctly conical above than the P. Hebe — the volutions 

 being rounded without the angle on the periphery. It was originally described 

 as Pleorotomaria, which it resembles in form, but has no proper peripheral band. 

 Other specimens coming under examination, it was properly referred to the 

 genus Cyclonema, and thus published as a new species in Illustrations of Devonian 

 Fossils, as cited above. A comparison with the original of P. Doris has proved 

 the identity of the two. From the examination of a single imperfect specimen 

 from the Schoharie grit, it seems probable that the figures given are from 

 specimens which are more or less accidentally depressed, and that the spire is 

 more elevated than represented. 



Formation and locality. In the Schoharie grit of the Upper Helderberg 

 group, at Schoharie, N. Y. The occurrence of the species in the Corniferous 

 limestone {Fifteenth Rep. State Cab.) has not been verified by farther investigation. 



Cyclonema lirata. 



PLATE XU, FIGS. 27-20. 



Cyclonema lirata, Hall. Descriptions of New Species of Fossils, etc., p. 19. 1861. 



» « Fifteenth Rep. N. Y. State Cab. Nat. Hist., p. 47, pi. 5, fig. 15 (not 16). 1862. 



«• " " Illustra'ions of Devonian Fossils : Gasteropoda, pi. 12. 1876. 



Shell robust, subdepressed-conical. Volutions about four, subangular, the 

 last one becoming very ventricose, flattened from the suture to the first 

 carinate elevation on their upper side, and marked by moderately elevated 



