66 Annelida Chcetopoda 
illary setae of the anterior segments (f. 150), evidently 
agree better with Laonome than with Potamilla. The 
ordinary form of capillary setae on the posterior segments 
is shown in f. 153, but there are a few with narrower mar- 
gins, and also some with a single margin, similar to f. 149. 
Body of nearly uniform size, a few of the last segments 
tapering slightly. 
This species lives in tortuous galleries excavated in 
compact shells, lined with a delicate membrane, which 
projects from 6 to 10™"". No entire specimen was obtained. 
They could not be withdrawn without breaking, and it 
was difficult to follow the galleries, owing to their tortuous 
course and to the compactness of the shells. 
A nearly entire specimen, having 100 segments, was 
15"" in length; width not quite l"". Color, reddish-brown 
above, white below. 
This species lives in colonies, and scattered among 
them were frequently found individuals with only three 
pairs of branchiae, light red, without eyes, quite short and 
narrow. As in all other respects they agree perfectly with 
the species described above, they may be the young of 
that form. 
I have referred this species to Potamilla 31grn., although 
it does not agree with that genus in all respects. The 
ventral sulcus is certainly continued on the dorsum. The 
form of the shorter capillary setse has been already referred 
to. Aside from these points it agrees with Potamilla. 
Fam. SERPULID^. 
HYDROIDES Ounnerus. 
Hydroides dianthus Verrill. 
Serpula dianthus Vehr. Invert. An. Vin. Sound, etc., p. 620. 
Hydroides dianthus Veru. In Notes on the Nat. Hist, of Fort Macon, N 
C, Coues and Yarrow (No. 5), in Proc. Acad, 
Nat. Sci. PMla., 1878 (advance sheets;. 
