. GASTEROPODA. 137 



Formation and localities. In limestone of the age of the Upper Helderberg 

 group at the Falls of the Ohio, and at other places in Indiana and Kentucky. 

 Some of the larger casts of Gasteropoda, occurring in the same formation in 

 New York and Ohio, are probably of this species. 



NOTE ON EUOMPHALUS DECEWI. 



On page 56 reference has been made to a specimen of this species, com- 

 municated by Dr. Rominger, which is illustrated on plate 27, figures 1, 2 

 and 3. The specimen has been covered on the lower side by an overgrowth 

 of Stromatopora, and the mouth is filled by the same parasitic growth which 

 had overlapped the upper and inner side of the volution near the aperture. 

 Besides this enveloping body, the upper and lateral portions of a part of the 

 outer volution have been covered by a Bryozoan which has left its markings, and 

 partially its substance, as shown in the figures. The removal of the Stroma- 

 topora from the lower side has destroyed the markings of the shell, except 

 upon a small portion of the surface, as seen in figure 2. The shell has been 

 somewhat compressed in a vertical direction ; otherwise, it preserves its proper 

 proportions. In consequence of this vertical compression, the baso-lateral 

 angle has been expanded into a kind of projecting carina, as shown in figures 

 2 and 3. 



This shell presents characters not before suspected from an examination of 

 the casts, which is the only condition in which the fossil was for a long time 

 known. Recently the surface markings of the upper side have been illustrated 

 in figures given in the reports of the Geological Survey of Ohio : Paleontology, 

 vol. 1, plates 19 and 20. While possessing the form and general features of 

 Euomi'ii \ i. is, this fossil presents an aperture of peculiar character, being 

 broadlv expanded, and somewhat quadrangular on the lower side, and triangular 

 as seen directly in front. The upper margin is sharply sinuate, making a deep 

 retral angle which meets a strong peripheral band, as in Pleurotomaria ; but 

 instead of being on the side of the volution, as in that genus, it is upon the 

 summit : in all other respects the characters of the band are the same. This 

 feature is not altogether properly represented in the figure. The appearance 

 18 



