ON ANNELIDA. 
105 
lier of the enlarged extremity of the proboscis ; more fre- 
quently it is furnished with folds, with tubercles, or even with 
tentacular papillae at its orifice. 
Finally, in the multidcntated species, the mouth, as has 
been already mentioned, presents the disposition of a cleft, at 
the orifice of which the whole of the jaws may be supported 
by the muscles which move the whole buccal mass ; these 
jaws appear to be nothing but the corneous or calcareous en- 
crustment of longitudinal folds to the number of three or four 
on each side, wider, and more open in front, narrower, and 
convergent one towards another behind. Accordingly, they 
always seem to be of the same number on each side ; but the 
first two folds, the most anterior and inferior, much shorter 
than the others, are sometimes composed of two corneous or 
calcareous particles, placed one at the end of the other. 
This anomalous disposition has occasioned MM. Savigny and 
Lamarck to attribute to these animals jaws of uneven numbers, 
and always more numerous on the left than the right. In an 
individual of the nereis pinnata, examined by M. de Blain- 
ville, there were four teeth, the first anterior and inferior one 
was semi-lunar, very small, simple on the right hand, and with 
a small tubercle at the posterior angle on the left; the second, 
a little larger, and of the same form, but denticulated on its free 
edge, was in like manner undivided on the right, and divided 
on the left, the accessory part being in front of the principal. 
Finally, the other two were perfectly similar on both sides : 
one broader, stronger, and denticulated on its free or internal 
edge, was joined to the fourth, which was longer, more slender, 
and more posterior ; for its posterior third part, and beyond 
that this double tooth, united on a common pedicle, is con- 
tinued with its corresponding one of the opposite side, some- 
thing like a pair of sheers, and it was this part which was 
principally seized by the thick annular muscle. In an indi- 
vidual of the nereis gigas, whose jaws had pretty nearly the 
