DORSIBRANCIIIATA. 393 



terminates behind into a tnbe recurved over the head, doubtless for the purpose of emitting tlieir excrements. I 

 have found in theni a muscular gizzard. 



Such upon our coasts is the Sabella alveoluta, Gnielin, or Tuhiporaarenosa, Linn., tlie tubes of which, united 

 into a compact mass, present orifices rather regularly disposed, like the cells of a honey-comb. The Amp/iilnfe 

 /'lutnosa, Fabr., should peiiiaps rano;e here, of which M. Blainville has formed his ^enus Pherusa. Amph. oatrcuriay 

 Cuv., establishes its tubes upon Oyster-shells, and is reputed to check the propagation of their inmates. 



To this order I suppose nuist be appro.\imated 



The Syphostoma, Otto, — 

 Wliich have a liundle of tine silky Ijristles above each articulation, a siiriple bristle l)clo\v it, and at the 

 lore 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 branchise, and which are 

 accompanied by two fleshy tentacles. Their medullary nervous cord may be sceu through the skin of 

 the belly. They live deep in the mud. 



The sjiecies are -S. diplocho'dea, Otto, and S. uncinata, And. and Edw. 



Lastly, in the vicinity of the same group, has lately been placed 



Dentaltum, Linn., — 

 The species of which have a shell in form of an elongated cone, arcuated, and open at both ends, 

 which maybe compared to an Elephant's tusk in miniature ; but 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 oi)ercuhnn, by wliich it closes 



the orifice. At the base of this foot is a small, flat head, and there are 



feather-like branchise upon the neck. If the operculum approximates the 



''' " " ' luijc. ' foot of the Tubulibranchiate Mollusks {Vn-metus and Siliquaria), tlie gills 



are rather those of AmpJiitrite and Terelella. 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. daphauthum, 

 Martini, &c. ; among the second, D. denlalis, Runipf. ; and among the third, D. enlalis, Martini. 



THE SECOND ORDER OF ANNELIDES,- 



THE DORSIBRANCHIATA,- 



Have tlicir organs, and particularly their gills, distributed about eciually tlirougbout tlie 

 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 arbuscnlar form, upon the rings of the middle part of the body only. The mouth a fleshy 

 tnmk. more or less dilatable, but no discernible teeth, tentacles, or eyes. Tlie posterior extremity of 

 the linilv devoid not only of gills, but also of bundles of silky bristles, which occur on the other part ; 

 no cirrlius on any ring of the liody. M. Savigny forms of them his family Thele'Diuces. 



The common species {Lumbyicus mariitus, 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 f|uantily of yellow fluid. It has three pairs of gills. 



Amthixome, Brng. 



A pair of branchire in form of a crest, or a tuft more or less complicated, on each ring of the body, 

 and two bundles of separate bristles, together with two cirrhi, upon each foot. The trnnlt or proboscis 

 witliout jaws. These form the family of Jmphinonirs of M. Savigny, who divides them into 



Chloela wherein are five tentacles to the head and gills in form of a tripiunate leaf. There is one in the East 

 Indies {Tereie'.ia flora, Gm.), extremely remarkable for its long citron-coloured bundle of bristles, and for its 

 splendid purple tufts of branchiie. Its form is broad and depressed, and it has a vertical crest on the muzzle. 



