GASTEROPODA. 6 3 



It differs from the E. inops in a more gradual enlargement of the volutions, a 

 more regularly convex surface on the lower side, and a shallower umbilical 

 depression. 



Several of the specimens are decollated, and the inner volution rounded 

 at its upper extremity as if terminated by a septum. A similar feature has been 

 noticed in E. Decewi. The species under consideration has none of the aspects of 

 a Cephalopodous shell, except in this single feature ; and no evidence of septa can 

 be seen in any part of the shell below the smooth, rounded, upper extremity. 



Formation and localities. In the Schoharie grit at Schoharie, N. Y., and in 

 the upper Helderberg limestone, near Cayuga, Ontario. 



The small group of species of Euomphalidae above described, present many 

 characters in common with those described by d'Archiac and de Verneuil, 

 from the older deposits of the Rhenish Provinces ; and notably among those 

 may be mentioned E. lavis, E. planorbis, E. annulatus (E. annulosus, Philips,) and 

 E. serpula, de Koxixck. The last named is cited as occurring also in the moun- 

 tain limestone of Belgium and Ireland. The same group of species is illus- 

 trated by Goldfuss (Petrcfacta, vol. iii), and cited as occurring in the Eifel 

 Nassau, etc. As already stated, tbe E. Wahlenbergii is closely allied to E. De- 

 cewi, and the figures alone do not offer sufficient evidence of specific distinction. 



De Koninck recognizes, essentially, the same group of species in the carbon- 

 iferous rocks of Belgium {Descriptions des Animaux Fossiles qui si Trouvent dans 

 le Terrain Carboniftre de Belgique). 



Sandberger has recognized the E. annulosus, E. lavis, d'A.-de V., E. rota, 

 Sand., and E. serpula, associated with other Gasteropoda and Cephalopoda of 

 similar character to those of our Upper Helderberg, Hamilton and Chemung 

 groups {Die Versteinerungen des Rheinischen Schichtensystems in Nassau). 



The species figured on plates 15 and 16 of this volume, are distributed 

 through a vertical thickness of about three thousand feet. Similar forms occur 

 at the base of the carboniferous rocks in Iowa, Illinois and Missouri, and espe- 

 cially in the yellow sandstone of Burlington, and the succeeding limestones. 



