ON ANNELIDA. 105 



ner 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 multidentated 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 conieous or calcareous en- 

 crustment of longitudinal folds to the number of three or four 

 on^ each side, wdder, and more open in front, nan'ower, 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 foui'th, 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 



