16 
CLASS ANNELIDA. 
Sypliostoma, Otto , 
Which have at each articulation, superiorly, a bundle of fine 
hairs, inferiorly, a simple seta , or bristle, and at the an- 
terior extremity two parcels of strong and gilded bristles. 
Under these bristles is the mouth, preceded by a sucker, sur- 
rounded with many soft filaments, which may perhaps be 
gills, and accompanied by two fleshy tentacula. The knotted 
medullary cord is observable through the skin of the belly. 
They live embedded in mud. — SipJiostoma diplochaifes, Otto; 
Siph. uncinata , Aud. et Edw. Littoral, de la France, Annel. 
pi. ix. fig. 1 . 
Hitherto has always been placed in this vicinity — 
Dentalium, 
Which have a shell like an elongated cone, arched, open at 
the two ends, and which has been compared to an elephant’s 
tusk in miniature. But the recent observations of M. 
Savigny, and especially of M. Deshayes, render this classifi- 
cation very doubtful. See “ Monographic du Genre Dentate , 
Mem. de la Soc. d’Hist. Nat. de Paris,” t. ii. p. 3*21. 
This animal does not appear to have any sensible articula- 
tion, nor lateral seta ; but it has a membranous tube in front, 
in the interior of which is a sort of foot, or fleshy and conical 
operculum, which closes its orifice. On the base of this foot 
is a small and flailed head, and gills in the form of plumes, 
and visible in the nape. If the operculum remind us of the 
foot of the vermeta and siliquarice , which have been placed 
among the mollusca, the gills strongly remind us of those of 
the Amphitritm and Terebellae. Ulterior observations on their 
anatomy, and principally on their nervous and vascular sys- 
tem, will resolve this problem. 
Some of these have the shell angular, or longitudinally 
striated. — Dent . Elephantinum , Martini ; I. i. 5. A. ; D . 
