56 COMPARATIVE ZOOLOGY. 
and carries within it a rasp-like tongue, which can bore 
into the hardest shells. Such as feed on vegetable matter, 
) as the Snail, have no probos- 
cis, but on the roof of the 
mouth a curved horny plate 
fitted to cut leaves, etc., which 
hia. i8.—Jaw of the Common Snaii are pressed against it by the 
as lips, and on the floor of the 
mouth a small tongue covered with delicate striz. As 
fast as the tongue is worn off by use, it grows out from 
the root. 
The mouth of the Cuttle-fish strikingly resembles that 
of the Vertebrates, and is the most elevated type below 
the Fishes. A broad circular lip nearly conceals a pair 
of strong horny mandibles, not unlike the beak of a par- 
rot, but reversed, the upper mandible being the shorter of 
the two, and the jaws, which are cartilaginous, are imbed- 
ded in a mass of muscles, and move vertically. Between 
them is a fleshy tongue covered with papillee and spines. 
The parasitic Worms, living within or on the outside 
of other animals, generally have a sucker at one end or 
underneath, serving simply for attachment, and another 
which is perforated. The latter is a true suctorial month, 
being the sole inlet of food. It is often surrounded with 
hooklets or teeth, which serve both to scarify the victim 
and secnre a firm hold. In the Leech, the mouth is a 
triangular opening with thick lips, the upper one prolong- 
ed, and microscopic teeth. In many Worms it is a fleshy 
tube, which can be drawn in or extended, like the eye- 
stalks of the Snail, and contains a minute dental appara- 
tus inside. 
Millepedes and Centipedes have two lateral jaws and a 
four-lobed lip. 
In Lobsters and Crabs, the mouth is situated underneath 
the head, and consists of a soft upper lip, then a pair of 
