DORSIBKANCHIAT.E. 133 



The shell of some of them is angular *, or longitudinally striated f . 

 That of others is round J. 



ORDER II. 



DORSIBRANCHIATJE. 



The organs of the Dorsibranchiatae, and the branchiae in parti- 

 cular, are equally distributed along the whole of tlie body, or at least 

 of its middle portion. 



At the head of the order we will place those genera in which the 

 organs are most completely developed. 



Arenicola, Lam. § 



Branchiae, resembling small trees, on the rings of the middle part 

 of the body only : the mouth, a fleshy and more or less dilatable pro- 

 boscis; and have neither teeth, tcntacula nor eyes, visible. The posterior 

 extremity not only wants the branchiae, bxit the setaceous fasciculi 

 with which the rest of the body is furnished ; the cirri totally de- 

 ficient. 



Aren. piscatorum. Lam.; Lumbricm viarinus, L. ; Pall. Nov. 

 Act. Petrop., ii, 1, 19 — 29. Very common in the sand on the 

 sea-shore, where it is disinterred by the fishermen, who use it as 

 bait. It is about a foot long, of a reddish colour, and diffuses 

 an abundant yellowish liquid when touched. It has thirteen 

 ]>airs of branchiae ||. 



Ampiiinome, Brug.*i\ 



A pair of more or less complex, tufted or plumose branchicc on each 

 ring of the body, and to each of the feet two fasciculi of separate 

 setae, and two cirri ; no jaws to the proboscis. The Amphinomes 

 are divided by M. Savigny into 



* Dent, elephantium, Martini, I, 1, 5, A; — Dent, aprinum, lb., 4, A ; — D. stria- 

 tuh'm, lb., 5, B ; — D. arcuatum, Gualt., X, G ; — D. sexangulum. 



t Dent, dentalis, Rurapf., Mas., xli, 6 ; — D. fasciatum, Martini, Condi., I, 1,3, 

 B;— D. rectum, Gualt., X, H, tkc. 



X Dent, entalis, Martini, I, i, 2, &c. 



§ M. Savigny has made a family of this genus by the name of Thelethus^, 

 which has been adopted by his successors. 



II Add, Arenicola clucaUi, Ranzani, dec. I, p. 6, pi. i, f. 1, should it prove to be a 

 distinct species. 



^ This genus has very properly been withdrawn by Brugi^res, from the Aphrodit.e 

 of Pallas and the Terebell.e of Gmelin. It forms the type of M. Savigny's 

 family of the Amphinom^, also adopted by his successors. 



