[617] INVERTEBRATE ANIMALS OF VINEYARD SOUND, ETC. 323 
the next have three or four branches; farther back they divide dichotom- 
ously above the base into numerous branches, all of which are supported 
upon a short basal pedicel, which may be a little elongated in expansion, 
the total length of the branchiz being then greater than the diameter of 
the body; the branches are clustered, slender, delicate, and elongated, 
and each one is terminated by a small fascicle of slender, sharp, serrate 
setze two to four or more in a group, so that the entire appendage may 
. be regarded as a very remarkable enlargement and modification of the 
setigerous lobes of the “ feet.” 
On the segments anterior to the ninth the setigerous lobes of the feet 
are short, conical, swollen at base, and bear a small fascicle of sete; the 
ventral surface of the anterior segment is somewhat raised, and divided by 
a series of sulci or wrinkles into several lobes or crenulations, which are 
somewhat prominent and papilliform at the posterior margin of each 
segment, and havea granulous surface. There isa distinct median ven- 
tral sulcus. Between the adjacent branchial cirri anteriorly there are, 
on each side, four or more thickened, somewhat raised, squarish organs, 
with a granulous and apparently glandular structure; farther back these 
are reduced to two, then to one, and finally disappear on the segments 
of the posterior region, which is very long, slender, attenuated, composed 
of very numerous short segments, with only rudimentary appendages ; 
after the branchial cirri become reduced to simple processes they still con- 
tinue, on about forty segments, gradually decreasing in length and size; 
beyond this small setz still exist on the segments, till near the end of the 
body. Anal segment small and simple, the orifice with slightly crenu- 
lated margins. Frontal membrane large and broad, versatile in form, 
often with a deep emargination in front, each lateral lobe divided into 
two or three subordinate lobes, or unequal scollops, the edges undulated ; 
at other times the front edge and sides are broadly rounded and entire. 
The mouth is furnished with a large elongated ovate lobe, which is 
rounded, free, and prominent posteriorly. Tentacles very long, much 
crowded, and very numerous; in extension usually as long as the body. 
Color of body, anteriorly, deep blood-red; posteriorly, more or less mot- 
tled or centered with yellow, owing to the internal organs showing 
through the integument; tentacles and branchial cirri bright blood-red. 
Length up to 350™™ ; diameter 5™™ to 7™™ or more anteriorly ; length 
of tentacles, in extension, 400™™ or more. 
Great Egg Harbor to New Haven and Vineyard Sound; common at 
low-water mark, in mud. 
POTAMILLA OCULIFERA Verrill. Plate XVII, fig. 86. (p. 322). 
Sabella oculifera Leidy, op. cit., p. 13 (145), Plate 11, figs. 55-61, 1855. 
Great Egg Harbor to New Haven; Vigeyard Sound, low-water mark 
to 25 fathoms, off Buzzard’s Bay. Inthe Bay of Fundy from low-water 
mark to 60 fathoms. 
Closely related to P. reniformis of Northern Europe, and possibly iden- 
tical with it. 
