ASSIMINIA. 
21 
sessile, on the outer side of the base of the ten- 
tacles; jaws horny; teeth in 7 longitudinal series, 
converging. Mantle-edge simple. Gill single, 
formed of very numerous flat free cross-folds, 
occupying nearly the whole of the inner sur- 
face of the cavity. Foot moderately broad for 
walking. Opercular lobe simple. Operculum 
spiral, horny, of gradually enlarging whorls. 
Amphibious ; marine, or in brackish water. 
1. Assiminia Leach MS. (Assiminia.) 
Shell ovate, conical, solid; mouth ovate; tentacles 
simple, very short, scarcely longer than the tu- 
bercles on which the eyes are placed, and united 
to their side ; operculum horny, ovate, of a few 
rapidly enlarging whorls, (p. 23. f. 3.) 
The animal differs from Littorina in the apparent 
position of the eyes, which is an anomaly among the 
water or Ptenobranchous Mollusca. 
This animal was first indicated, and its peculiari- 
ties pointed out, in my paper above quoted, ini 821 
when I made the following remarks on its structure. 
The animal of this shell differs from all others of 
the order (to which it belongs), by the eyes appear- 
ing to be placed at the end of the tentacle ; but I 
believe that they are placed on a peduncle as long 
as the tentacle, and the peduncles and tentacula are 
soldered together.” 
Mr. Berkeley, in his description of the animal 
{Zool. Journ. v. 429.), observes, — The most re- 
markable circumstance in this animal is the position 
