No. lOtl.] 149 



Branchice begin on seventh segment, long, finger-shaped, color- 

 less, with red center ; tliey are found on all segments after the sixth, 

 except a small but variable number of posterior segments. 



Seta3 of the fifth segment (lig. 46) eight to twelve in number, 

 stout, apex bluntly rounded and slightly curved; a little below the 

 apex is a small tooth on the side of the seta; forming a very small 

 angle with the seta ; dorsal setrei long, capillary, longer behind than 

 in front ; ventral seta? (fig. 47) short, bidentate ; inner tooth very 

 long, sharp, given off at right angles to the body of the seta ; outer 

 half covered by a membrane. 



Terminal sucker broad, shallow, white ; anal opening surrounded 

 by low papillae. 



Body colorless, except as colored red or brownish-red by the blood 

 and contents of the intestine ; on either side of the carina a brown 

 line, diverging in front, and passing to the outer base of the tentacles. 



Length, 1-4""" ; segments numerous. 



Found on water-soaked wood, living in crevices, etc. 



Tubes made of dirt, fragile, constructed with great rapidity. 



STREBLOSPIO 7i. gen. 



Head conical ; proboscis incomplete above, divided below into 

 two lobes along its anterior part. First segment prolonged laterally 

 and below nearly to the front of the head ; above carrying one pair 

 of tentacles and one pair of branchi^. Second segment with raised 

 dorsal membrane, forming a pouch. Dorsal set?e capillary. Ven- 

 tral set?e of first six segments like the dorsal, afterward both un- 

 cinate and capillary. Anal segment simple, without appendages. 



Steeblospio Benedicti n. sp. 



PLATE (v), viii, FIGS. 48-50. 



Head, in extension, pointed, conical ; posterior half somewhat 

 compressed, sharply convex ; anterior half slightly depressed. 



Proboscis deficient above, below divided into two lobes for about 

 one-half its length ; these lobes are triangular at base, but (in ex- 

 tension) terminate, each in a short, finger-shaped process, covered 

 with numerous long cilia. The first segment is about the length of 

 the following segments, dorsally ; at the sides and below it is pro- 

 longed, forming a kind of hood for the head. This hood or sheath 

 originates as a thin, almost membraneous elevation of the sides of 

 the segment, just within the dorsal setre, passes forward external to 

 the bases of the tentacular cirri and branchia?, is prolonged to near 

 the apex of the head, then curves suddenly downward, presenting a 

 rhin, free, anterior margin ; laterally it is closely applied to the 

 head, l)ut rises above it, presenting a free, upper margin on each 

 side ; the head projects but very little beyond its hood. Dorsally 

 the anterior margin of the first segment is concave, and carries a 

 minute, conical, median papilla or cirrus. 



Tentacular cirri (tentacles) have the same structure as in Poly- 

 DORA ; turned backward they reach to the eighth or ninth segment. 



