DORSIBRANCHIATA. 393 



terminates behind into a tube recurved over the head, doubtless for the purpose of emitting their excrements. 1 

 have found in them a muscular gizzard. 



Such upon our coasts is the Sabella alveolata, Gmelin, or Tubiporaarenosa, Linn., the tubes of which, united 

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

 plumosa, Fabr., should perhaps range here, of which M. Blainville has formed his genus 1'herusa. Amph. ostrcaria, 

 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 

 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 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 8. diploehoitm, Otto, and .<?. 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 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 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 



Fig 302. — DentaUnm entdli, in in ,..„.,., , . ■.,,,,/ ,. , , r.... . \ , ... 



tube. foot of the rubuhbrancbiate Mollusks {I ermetus and Sdiquana), the gills 



are rather those of Amphitrite and Tercbdla. 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, D. etitalis, Martini. 



THE SECOND ORDER OF ANNELIDES,— 



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. 



Arkmcola, Lam. 



1 i" an urbuscular form, upon the rings of the middle part of the body only. The niouth 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 OCCUI 00 t he other part ; 

 no cirrhus on any ring of the body. M. Savigny forms of them his family Tin Irt Inters. 



The common species [Lumbriau mm- inn a, Linn.), is very abnndanl In the sand of the sea shore, where the 

 '"i-Im rmeii dig for it tn serve as bait. It is nearly a foot long, of a reddish colour, and diffuses, on being touched, 

 :i qnantit] OfyellOX fluid. It has three pairs of gills. 



A.MPHINOME, Hnig. 



\ pair of branchiae in form of a crest, or a tuft inure or less complicated, on each ring of the body, 

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

 without jaws. These form the family of Amphmomei "t" M. Savigny, who divides them into 



Chloeia, « herein sre Ave tentacles to the head and gills in form of s tripinnste leaf Then- is one in the l tl 

 Indies {TerebeOaflava, Gin.), extremely remarkable for its long citron-coloured bundle of bristles, snd far its 

 splendid purple tuft* of branchlsj. Its form is broad and depressed, and it bus a vertical crest on themusxle. 



