LUNG-BREATHING MOLLUSKS. 83 
the mud at the mouths of rivers, or in the sea: 
they seldom leave salt, or at least brackish water. 
There are some foreign species which live in ponds, 
and have all the habits of our Pond-snails, only 
that their pillar is more distinctly plaited. 
The family may be represented by Conovulus 
denticulatus, an oblong, spiral shell, rarely exceed- 
ing half an inchin length, of a brown or purplish hue. 
Its last whorl is long and compressed ; the pillar is 
grooved, with several spiral plates; the throat is 
also grooved. A remarkable character of this shell 
is, that the pillar extends no further than the upper 
part of the last whorl, the upper whorls being des- 
titute of any pillar or internal spiral division. 
This character is common to most species of the 
family, and forms, as Mr. Gray observes, one of 
its best technical distinctions. It is attributed to 
the animal’s absorbing the partitions which separate 
the upper whorls, and thus converting the spire into 
a single cavity. 
This little Mollusk is by no means common ; it 
has been found in the marshes near Faversham, at 
the roots of rushes. It ) 
is said also to inhabit 
the clefts of rocks, near 
high water-mark, as well 
as the mud left bare by 
the tide, at the mouths 
of rivers. The animal A 
feeds, according to M. THE DENTICULATED CONOVULUS. 
Bouchard Chantreux, (Nat. size and magnified.) 
on the detritus of marine plants and rotten wood. 
It lays twelve or thirteen eggs in the months of 
June and September, united by a viscid matter 
into a small mass, which is fixed under the more 
