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: Palaeontology , 
vol. 1, plates 19 and 20. While possessing the form and general features of 
Euomphalus, this fossil presents an aperture of peculiar character, being 
broadly 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 
