INVERTEBRATE ANIMALS OF VINEYARD SOUND, ETC. 617 



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 branchiae 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 

 setae 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 setae ; 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 have a granulous surface. There is a 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 j 

 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 setae 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 mm ; diameter 5 mm to 7 mm or more anteriorly ; length 

 of tentacles, in extension, 400 mm or more. 



Great Egg Harbor to New Haven and Vineyard Sound ; common at 

 low-water mark, in mud. 



Potamllla 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 ; Vineyard Sound, low-water mark 

 to 25 fathoms, off Buzzard's Bay. In the Bay of Fundy from low- water 

 mark to 60 fathoms. 



Closely related to P. reniformis of Northern Europe, and possibly iden- 

 tical with it. 



