ORDER DOR SI BRANCH I A. 
17 
aprinwn , ib. 4. A. : 7). striatuliim , ib. 5. B. ; 11. arcuatum , 
Gualt. x. G. ; D. sexangulum . Dent . dent alls, Humph. Mus. 
xli. 6 ; Zl. Fasciatum Martini , Conch, i. 1. 3. B. ; H. rectum , 
Gualt. x. H., &c. 
Others have round shells : Dent . entalis , Martini, I., i. L 
&c. 
SECOND ORDER OF ANNELIDA. 
THE DORSIBRANCHIA, 
Have their organs, especially their gills, distributed pretty 
equally along their whole body, or at least along its middle 
portion. 
We shall place at the head of the order, the genera whose 
gills are the most developed. 
Arenicola, Lam., 
Have gills in the form of arbuscula, on the rings of the 
middle part of their body only ; their mouth is a fleshy 
proboscis, more or less dilatable, and neither teeth nor tenta- 
cuia, nor eyes are visible. The posterior extremity is not 
only destitute of gills, but also of the parcels of silky hairs, 
which furnish the rest of the body. No cirrhus exists to any 
ring of the body. 
M. Savigny has made of this genus, a family which he names 
Thelethusa , and which has been adopted by his successors. 
The known species, Aren . piscatorum , Lam., Lumbricus 
marinus , L. Pall. Nov. Act. Petrap. II. i., is very common on 
the sand on the sea-shore, where the fishermen go in search 
of it with spades, to use it as a bait. It is about a foot long, 
of a reddish colour, and diffuses, when it is touched, an 
abundant yellowish fluid. It has thirteen pairs of gills. Add. 
VOL. XIII. V 
