SUPPLEMENT ON GASTEROPODA. azo 
of white sinus of no great depth, surrounded with tubercles, 
and which exists at the posterior part of the back of the red 
limaces. Into the thickness of this skin, it appears from 
desiccation, that there enters a great number of calcareous 
molecules; but they exist in much greater quantity in the 
anterior part of the body, sometimes called the shield, so as to 
form, especially in the grey limaces, the rudiment of a shell, 
which it is true, is very thin. 
The viscous matter just mentioned serves to attach the 
limaces to the bodies over which they move. By means of 
this sort of spittle, become friable and shining, a limax may 
be traced, frequently many days after it has passed. To- 
bacco, common salt, and in general all irritants, produce so 
great an ejection of this matter, that the animal swells, stiffens, 
and dies, when a pinch of them is put upon its head. 
These animals have four tentacula. The extremity of the 
anterior is swelled, translucent, and as it were gelatinous. 
That of the posterior tentacula presents a small disk, alto- 
gether black, which forms the organ of vision. The eye, very 
small, is nearly spherical. It has evidently a fibrous enve- 
lope, very thin, and allowing the black colour of the choroid 
to be seen through. Behind, the sclerotica is applied against 
the nervous ganglion; in front itis continued with the trans- 
parent cornea, which appears also to be the continuation of 
the skin. ‘The choroid, very much coloured, is pierced by a 
pupil extremely small. 
The organ of locomotion, as in all animals of the molluscous 
type, is in a great measure cutaneous, that is, the muscular 
fibres which compose it, are very adherent to the skin, con- 
founded with the dermis, and disposed in all directions. 
Under the belly, however, where the locomotive disk exists, 
they are much thicker, and directed according to the length 
of the animal. 
The tentacula are hollow in all their length, and formed by 
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