DOR8IBRANCHIATJB. 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 the body, or at least 

 of its middle portion. 



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

 rgans 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, tentacula nor eyes, visible. The posterior 

 extremity not only wants the branchiae, but the setaceous fasciculi 

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

 ficient. 



Aren. piscatorum, Lam.; Lumbricus marinm, 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 

 pairs of branchiae ||. 



AMPHINOME, Brng.^l 



A pair of more or less complex, tufted or plumose branchiae 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, tlfphantium, Martini, I, 1, 5, A; Dtnt. aprinum, Ib., 4, A ; D. stria- 



Ib.. 5. II : I), nrcuatum, Gualt., X, G ; D. sexangulum. 

 f Dent, dentalis, llumpf., Mus., xli, 6; D. fasciutum, Martini, Conch., I, 1, 3, 

 B; D. rectum, Gualt., X, H, &c. 

 t Dent, entalu, Martini, I, i, 2, &c. 



M. Savigny has made a family of this genus by the name of THELETHUSA, 

 which has been adopted by his successors. 



|| Add, Arenicola clacata, Rauzani, dec. I, p. 6, pi. i, f. 1, should it prove to be a 

 distinct species. 



51 This genus has very properly been withdrawn by BruguVes, from the APHRODITES 

 illas and the TKRKBELI..K of Graclin. It forms the type of M. Savigny's 

 family of the AMI-HINOM.*, also adopted by his successors. 



