106 SUPPLEMENT 



same form, with the difference of being calcareous, the same 

 gentleman found that at the right the second tooth was equally 

 ditomous, the accessory piece being also in front. But be- 

 sides these sorts of lateral jaws in this section of nereides, 

 there is a sort of lower jaw, composed of two symmetrical 

 pieces, a little widened into a palate at the extremity, and 

 approximated in the medial line ; their posterior extremity 

 is implanted in the transverse fasciculus of muscular fibres 

 of the buccal mass. 



The communication of the mouth with the rest of the intes- 

 tinal canal is direct in the proboscidian nereids, but in the 

 unidenticulated species, and particularly in the multidcnticu- 

 lated, this is not the case. The buccal cavity forms a sort of 

 cul-de-sac behind, and the continuation is made with the oeso- 

 phagus, by an aperture in the form of a cleft, situated at the 

 anterior part of the superior paries. This orifice conducts 

 into a sort of pharynx, or enlargement, from which issues the 

 intestinal canal. The latter is always extended in a right 

 line, from one extremity to the other of the body of the ani- 

 mal. We often distinguish there a somewhat short oesopha- 

 gus, but much more narrow than the rest, as in the uniden- 

 tated species, and moreover some salivary glands, pretty 

 long, and a little twisted, and they open considerably behind 

 the buccal mass. The stomach, which is of a pretty con^ 

 siderable diameter, and almost equal to that of the abdominal 

 cavity, is sometimes without very distinct enlargements, and 

 corresponds to the rings of the body. It is sometimes pretty 

 markedly strangulated towards its grooves, and more or less 

 dilated into ccecal appendages in the enlargements of the 

 rings. Its parietes, often very slender, are sometimes, as in 

 the Nereis gigas, almost as thick as the skin, so that we may 

 easily distinguisli in them, as in the latter, two strata of fibres, 

 one longitudinal and the other transverse. Often also these 

 two parts of the general envelope are strongly connected toge- 



13 



