132 [Assembly 



denly backward, encroaching upon the anterior margin of the first 

 segment, the sides and front are regularly rounded, forming a semi- 

 circle. 



Antennse delicate, conical, length about one-half the width of the 

 head ; only the upper pair can be seen from above ; both pairs arise 

 from the lower surface of the head, upper also external and pointing 

 outward, lower directed downward. 



Eyes large, circular, lateral, posterior ; first segment prolonged 

 forward as far as the front of the eyes, embracing the sides of the 

 head. 



Tentacular cirri arise from short, stout basal articles, are stout at 

 base, regularly and acutely conical ; first and second equal, a little 

 shorter than the third, which reaches back to the front margin of 

 the fourth setigerous segment ; the fourth cirrus, or cirrus of the 

 second segment, as long as the third. 



Dorsal ch-ri (branchiae) broad heart-shaped (fig. 8), with long basal 

 attachment, retaining the same form throughout ; feet (fig. 8) 

 cylindrical, bilabiate ; ventral cirri with slightly convex lower 

 margin, nearly straight or slightly concave upper margin ; apex 

 bluntly rounded, a little shorter than the feet ; anal cirri circular, a 

 little thicker than the dorsal. 



Setse (fig. 9) long, slender, with very long and delicate appendix ; 

 the stem ends in two sharp curved points, one much longer than the 

 other. 



Color: head and first two segments white with brown specks; 

 dorsum generally dark green ; between the segments a narrow 

 spindle-shaped band of umber-brown ; eighth and ninth segments 

 umber-brown, giving a well-defined band of the width of these two 

 segments ; dorsal cirri green, not quite so dark as the dorsum, with 

 a central brown spot, extending to their attachment on the segments 

 3-9 ; after the ninth segment this marking becomes obsolete. Ven- 

 tral surface light green, growing darker externally, and with reddish- 

 brown lateral markings along the })Osterior third ; feet and ventral 

 cirri dark green at base, growing lighter further out. Anal segment 

 brown. The general color of the body in one instance was reddish- 

 yellow ; in another all the markings were very dark-brown, nearly 

 black, in place of the umber-brown. The transv^erse band on the 

 eighth and ninth segments is still visible, after six months' preser- 

 vation in very strong alcohol. Body slightly convex above, flattened 

 below ; the first segment is much wider than the second, but shorter ; 

 the second is narrower than the head ; the middle third of the body 

 has a uniform width, about double that at either extremity. 



Length of adult specimens, 10-12'"'" ; width, 1.5-2'"". 



Found occasionally at low water ; quite common on beds of 

 Mytilus edulis. 



