196 SUPPLEMENT 
animals. This swelling is regular and symmetrical, and re- 
ceives a considerable number of nerves. Its upper surface is 
most usually furnished with very small corneous hooks, the 
point of which is directed backwards, and which are disposed 
in a very symmetrical manner. These are again depend- 
ences, productions of the skin, but which cannot be compared. 
in consequence of their disposition and place to the marginal 
teeth. | 
This sort of tongue is never exsertile in front but along with 
the whole buccal mass, but it is sometimes prolonged in a 
singular manner behind, into the interior of the visceral 
cavity, being contorted like the spring of a watch. In ge- 
neral its disposition differs according to that of the teeth. 
In the species which have two teeth opposed, as in sepia, 
&c., the lingual plate is not very projecting nor very mobile. 
In those which have an upper tooth the lingual swelling is 
thicker, more mobile, but much shorter, and is easily carried 
forward by the motion of the adductor muscles. This may 
be seen in the limaces, helices, bulimus, limnee, &e. 
In the species which have no teeth whatever to the buccal 
orifice we find that the tongue forms a long narrow band, 
which is prolonged backwards into the abdominal cavity, 
rolling spirally. Its surface is bristled by a number of little 
hooks, bicuspid or tricuspid, directed backwards, and whose 
solidity or resistance, proceeds always decreasing from the 
base to the point, where they are soft and very little apparent. 
This singular kind of tongue is found in the porcelains, cones, 
patelle, and even in the oscabriones. 
Finally, in a great number of species which have no teeth, 
properly speaking, we observe that by a singular disposition 
of the cesophagus it may be prolonged externally or re-enter 
into the buccal cavity under the form of a cylindrico-conical 
organ, to which the name of proboscis has been given. Be- 
side the muscular dermis which. composes this organ, and 
