PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 177 



depressed, narrow iu middle, expanding laterally at the front, witli prom- 

 inent, blunt, lateral angles, and with a broadly rounded or sometimes 

 slightly emarginate front margin ; posteriorly the narrow head -lobe ex- 

 tends back to the second setigerous segment. Eyes four, minute, in a 

 quadrangle, the anterior pair wider apart. Antennai slender, not very 

 long, about three times as long as diameter of body. Buccal segment 

 swollen, forming short, convex, lateral lobes along the posterior half of 

 the head ; below the mouth is a prominent, strongly ciliated lobe. Bran- 

 chiae in four pairs, on the 2d, 3d, 4th, and 5th setigerous segments 5 the 

 anterior pair branched, the others ai)i)arently foliaceous and shorter.* 

 The first setigerous segment has a small, prominent, rounded, ujiper 

 ramus, with few short seta*. The 2d to 5th haAc a broad liuguliform, or 

 leaf-like, upper ramus, with the inner distal edge prolonged into an angle 

 over the back, and a very broad, fan-shaped fascicle of long acute setae 

 set transversely and protecting the gills ; a smaller lobe also exists in 

 front of the setae ; lower ramus composed of a small, rounded lobe with 

 a fascicle of slender setae, and with uncini in the fascicles beyond the 

 15th segment, and a cluster of acute setae. The parapodia increase rap- 

 idly in size from the 1st to the Gth, and then graduaUy decrease to the 

 17th segment, beyond which they are rudimentary ; on the 5th to 8th the 

 ui)per lingula is about half as long as the breadth of the body ; beyond the 

 5th they are more or less expanded distally, or wide, spatulato, bluntly 

 terminated ; beyond the 10th snmll, not very prominent, rounded; on 5th 

 to 10th segments the upper setae are slender, acute, longer than the lin- 

 gula, and in large fascicles, though in much smaller ones than those of 

 the branchiferous segments ; on the posterior segments the uncini become 

 longer, and the caj)illary setae mostly disappear in the lower fascicles. 

 Color yellowish or greenish white, often decidedly greenish posteriorly, 

 and with a dark greenish-yellow intestine. Some were filled with pale 

 pink eggs, August 29. 



Cape Cod Bay, 16 to 21 fathoms, soft, foetid mud (U. S. Fish Commis- 

 sion, 1879). 



Heterocirrus fimbriattis, sp. nov. 



A delicate species, remarkable for the great length and slenderness of 

 its setae, which form a wide fringe along the sides of the body. Head 

 small, about twice as long as broad, not half as broad as the body, ob- 

 tusely rounded in front, with a pair of subhiteral ocelli at about the 

 anterior third. Tentacular cirri short, usually absent in preserved speci- 

 mens. The three to six anterior segments bear each a pair of slightly 



* A larger spocimea w<as taken in 31 fathoms, oflf Capo Cod, which maybe a distinct 

 species. In this the branchiio are long, lanceolate, acute, and all are pectinately di- 

 vided along the posterior margin, with slender papilla?. The eyes are red. Proboscis 

 urceolate, with the extended margin scolloped. The first eleven segments bear capil- 

 lary setai, above and below, iu largo fascicles ; on the r2th to 16th there arc also 

 stouter acute spinules iu the lower fascicles ; beyoud the IGth segment there are un- 

 cini mingled with the capillary seta;. 



Proc. Nat. Mus. 79 12 JVov. 5, 1 879. 



