63 
ANCYLUS M idler. 
Gen. Char. Shell slender., patelliform, obliquely 
conical ; apex rather acute, turned back ; aper- 
ture oval, with an entire edge. 
A genus of small almost minute shells resembling Pa- 
tella, but differing in the form and direction of the apex, 
which takes a position indicating an incipient spire, 
and is not turned forward as in Patella. The recent 
species have a membranous epidermis. The animal 
resembles that of Limnea, living in fresh water, and 
breathing air, and is consequently very different from 
that of Patella ; it is attached to the shell along an 
involute line open on one side. 
Two recent species and two fossil ones are all that 
have hitherto been published. We now add a third 
fossil, which, although small, illustrates the genus well, 
and is consequently a valuable acquisition. 
