DORSIBRANCHIATA. 
393 
terminates behind into a tube recurved over the head, doubtless for the purpose of emitting their excrements. I 
have found in them a muscular gizzard. 
Such upon our coasts is the Sabella alveolata, Gmelin, or TuMpora arenosa, Linn., the tubes of which, united 
into a compact mass, present orifices rather regularly disposed, like the cells of a honey-comb. The Amphitriie 
plumosa, Fabr., should perhaps range here, of which M. Blainville has formed his genus Pherusa. Amph, ostreariat 
Cuv., establishes its tubes upon Oyster-shells, and is reputed to check the propagation of their inmates. 
To this order I suppose must be approximated 
The Syphostoma, Otto, — 
Which have a bundle of fine silky bristles above each articulation, a simple bristle below it, and at the 
fore extremity two bundles of stiff and gilded bristles, beneath which is the mouth, preceded by a 
sucker encircled by many soft filaments, that perhaps subserve the office of branchiae, and which are 
accompanied by two fleshy tentacles. Their medullary nervous cord may be seen through the skin of 
the belly. They live deep in the mud. 
The species are S, diplochoites, Otto, and S. uncinata, Aud. and Edw. 
Lastly, in the vicinity of the same group, has lately been placed 
Dentalium, Linn.,-— 
The species of which have a shell in form of an elongated cone, arcuated, and open at both ends, 
which may he compared to an Elephant’s tusk in miniature ; hut the recent observations of M. Savigny, 
and especially of M. Deshayes, render this classification very doubtful. 
The animal does not appear to have any appreciable articulations, nor 
lateral silky bristles ; but it has a membranous tube, in the interior of 
which is a sort of foot, or fleshy and conical operculum, by which it closes 
the orifice. At the base of this foot is a small, flat head, and there are 
feather-like branchiae upon the neck. If the operculum approximates the 
foot of the Tuhulibranchiate Mollusks {Vermetus and Siliquaria), the gills 
are rather those of Amphitrite and Terebella. Further observations on their anatomy, and principally 
on their vascular and nervous systems, are required to solve this problem. 
Different species have the shell angular, longitudinally striated, or round. Among the first are D. elaphantinum, 
Martini, &c. ; among the second, D, dentalis, Rumpf. ; and among the third, Z>. entalis, Martini. 
Fig. 202. — Dentalium entalis, in its 
tube. 
THE SECOND ORDER OF ANNELIDES,— 
I THE DORSIBRANCHIATA,- 
Have their organs, and particularly their gills, distributed about equally throughout the 
length of the body, or at least its middle portion. 
We place at the head of them certain genera, in which the gills are more developed. 
Arenicola, Lam. 
Gills of an arhuscular form, upon the rings of the middle part of the body only. The mouth a fleshy 
trunk, more or less dilatable, but no discernible teeth, tentacles, or eyes. The posterior extremity of 
the body devoid not only of gills, but also of bundles of silky bristles, which occur on the other part ; 
no cirrhus on any ring of the body. M. Savigny forms of them his family TJielethuces. 
I The common species {Lumhricus marinus, Linn.), is very abundant in the sand of the sea shore, where the 
fishermen dig for it to serve as bait. It is nearly a foot long, of a reddish colour, and diffuses, on being touched, 
a quantity of yellow fluid. It has three pairs of gills. 
j Amphinome, Brug. 
j A pair of branchise in form of a crest, or a tuft more or less complicated, on each ring of the body, 
|j and two bundles of separate bristles, together with two cirrhi, upon each foot. The trunk or proboscis 
without jaws. These form the family of Amphinomes of M. Savigny, who divides them into 
Chloeia, wherein are five tentacles to the head and gills in form of a tripinnate leaf. There is one in the East 
I Indies {Terebella flava,Gm.), extremely remarkable for its long citron-coloured bundle of bristles, and for its 
I' splendid purple tufts of branchiae. Its form is broad and depressed, and it has a vertical crest on the muzzle. 
