1288 Wisconsin Academy of Sciences, Arts, and Letters. 
Formation and Locality.—In the limestone of the age of the 
Niagara group at llaeine, Wisconsin. 
Type.—In the American Museum of Natural History, New 
York City. 
The figure shown on plate 01, fig. 1 is that of an external 
cast of the species described, showing seven volutions of the 
shell and which agrees in every respect \Ath the description of 
the type form, a little within what was the orifice or opening 
of the shell is found the impression of the operculum which had 
closed the opening and prevented the shell from becoming filled 
with sediment; the impression of the operculum is circular or 
slightly sub-ovate and is that of the outer surface which is ap¬ 
parently coiled upon its own axis and has about four volutions. 
Fig. 2, is that of the operculum in the form of which it is usually 
found, this also shows the outer surface on which the volutions 
are plainly shown and is the best preserved of the specimens 
collected. Figure 3, is of a similar specimen on one side of 
which is shown a raised edge by which we can judge the opercu¬ 
lum to have been about one-sixteenth of an inch in thickness. 
No specimens showing a satisfactory inner surface have been 
found, this surface, however, was probably smooth. 
Feh. 10, 1908. 
