SUPPLEMENT 
ON THE 
THIRD CLASS OF THE MOLLUSCA. 
THE GASTEROPODA. 
THIS class, though numerous, and divided into eight orders, 
we must embrace in a single supplement, as our object is now 
to confine ourselves as much as possible to popular matter. 
The first order is that of the PULMONARLA&, the first genus 
of which, LIMAX, we shall consider in a general manner, 
without attending to the subdivisions. 
The limaces in general, to which we give the name of 
slugs vulgarly, are naked mollusca, or at all events have no 
apparent shell. ‘Their organization exhibits a very great 
analogy with that of the helices or snails. 'The dermo-muscu- 
lar envelope, very thick, and especially in the under part, 
forms a long and simple cavity, in which the viscera are 
contained. ‘The dermis, which cannot be separated from the 
contractile stratum underneath, has a greater or less number 
of tubercles at its superficies. The colouring pigment at its 
surface is often very: thick, whereas the epidermis is very thin. 
A great number of pores are there distinguishable, which send 
forth a great quantity of mucosity to its surface. This ap- 
pears particularly to issue in greater abundance from a sort | 
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