MOLLUSCOUS ANIMALS. 
141 
Shell bluish, and the nodules white in some specimens. 
It is probable that Trochus melanostomus, Gmel. from Chem. v. t. 161. f, 1526/1527, will form a new 
section of this genus, characterised by being trochiform, and having a quadrangular mouth, with a sharp edged 
twisted concave callosity on the columellar lip ; to which will belong. 
Littorina australis. 
Shell trochiform, whitish, with irregular oblique transverse black bands ; whorls flat ; the last acutely 
keeled, slightly waved ; the suture indistinct, slightly nodulose, front of last whorl spirally subnodulosely ridged ; 
outer lip black spotted ; throat pale reddish brown. Axis 8; diam. lOlines. 
Inhab. New Holland. 
A very variable species. 
Littorina imbricata. 
Shell trochiform, brown, varied with white between the tubercles; front white, brown spotted ; whorls 
flat, with irregular large nodulose protuberances near the sutures, the last whorl flat and spirally grooved in 
front. Mouth ovate; outer lip varied with black; columellar lip and throat whitish. Axis 8 ; diam. 7£ lines. 
My collection. 
This species chiefly differs from the last in the large nodules near the sutures and in the colour : it may 
prove a variety of it. 
ASSAM 1X1 A. Leach , MSS. 
The tentacles short, thick, with the eyes on the outer side of their tip ; the foot ovate ; mantles and sides 
of the body simple; the operculum ovate, horny, spiral, of a few whorls. 
The shell is exactly like Littorina. 
This genus was established by Dr. Leach for a shell which I discovered in the Woolwich marshes in the 
year 1817. It is referred to by Dr. Fleming under the name of A. Grayana. Brit. Anim. 275; he places it 
at the end of Lymnea, and Mr. Jeffreys has referred it to that genus ! It is an instance of shells very 
nearly allied in external character having different animals. 
PAGODUS. 
The foot short, simple, sides of the body quite simple ; trunk short, annular ; tentacles conical, distant at the 
base; eyes on tubercles attached to their outer base; penis large, exserted, club-shaped, placed a little below 
and behind; the right tentacle conical and covered with minute spicula at the tip, and with two large spinose 
prominences, almost one-third down the hinder edge. The operculum suborbicular, thin, homy, of three 
or four rapidly enlarging whorls. ( Monodonta Pagodus. Lam.) 
PALUDINA. 
The gills are formed of a series of triangular plates attached to and forming an oblique line down the left 
side of the branchial cavity. 
There is an appendage on each side of the head, arising at the back of the tentacles, that of the left side is 
small, that of the right larger before. The hinder portion forms a canal as in Ampullaria. 
The muscle of attachment is double, the portion on the left side is the smallest. There is a similar ridge 
to that in Ampullaria, but the ridge up the back of the neck runs more to the left, and there is a large mass 
between it and the right edge of the body. 
Is the fat mass analogous to the bag in Ampullaria ? 
