216 CONTRIBUTIONS TO GEOLOGY. 
Observations. This species was obtained from the sand 
removed from the cavity of a large shell. In some of its 
characters, it answers the description of the planulata (Lam- 
arck). It differs from the savorum of Blainville, in having 
the lobes in contact, and in having the mouth terminal. 
In his figure it appears to be lateral. The most striking 
character of our species seems to be, that it possesses a 
large tooth, which partly fills the aperture. This, I be- 
lieve, has not been before observed in any described 
species. 
Lamarck describes four fossil species; three are from 
Grignon, and one from Louvres, near Paris. It has not 
before been observed, I believe, in this country. 
