PEDIPES. 301 
mals to the powers of an excellent microscope, I am enabled 
to say, that I found no traces of a regular pectinated mem- 
brane ; but when the dissection turned out well, there ap- 
peared, as in the Helices, what I considered to be the respira- 
tory cavity, having its walls led with an anastomosing net- 
work of vessels; one side of this membrane abutted on the 
rectum and the canal of the sac of viscosity. The strongest 
support that this is the true respiratory organ is, that I 
observed in several individuals large cylindrical masses, not 
pellets, of red-brown sandy fiecal matters, ejected from a 
dilatation in the mantle lining the aperture. It must not be 
supposed that I have mistaken this orifice for the termination 
of the rectum: that organ ends within the mantellar dilata- 
tion, exactly as in Helix, in which the respiratory orifice 
dilates to receive air as well as to emit the rejectamenta. This 
dilatation in the present species has not the aspect of the 
terminus of a rectum; it is a simple oblong fissure, which 
instantly closes and is lost to view when the feces are passed. 
The continual change of posture of these animals, not one of 
them $th of an inch long, prevented my observing the periodic 
dilatations. The facts I have stated appear to be decisive 
that the animal respires free air; in addition, it has the cord- 
like margin of the mantle, as in the Helices, around the 
aperture of the shell, and the figure and course of the large 
conspicuous intestine is also as in Helix. 
The animal when put into water instantly escapes there- 
from, apparently with the view of breathing free air. All 
the animals exhibited the ovary: this circumstance almost 
amounts to proof, that they possess a similar hermaphro- 
ditism to the Helices, that of mutual congression. Those I 
examined inhabited a bank wall, that for ten days out of 
thirty is covered by the sea for three or four hours out of the 
twenty-four ; they are found lying at the bottom of stones 
which are imbedded in a red sandy soil, and have not been 
disturbed for years; the detached stones at the base of the 
wall under which they are found are buried from 3 to 6 
inches, and require force to raise them. 
The fact that these animals are submerged for only a very 
