NO. 4 HARTMAN : POLYCHAETOUS ANNELIDS 433 



The epithelium of the thorax is smooth except for fine wrinkles of 

 contraction. The segments are only partly biannulate, a transverse groove 

 crosses the segments dorsally and at the sides between notopodia and neu- 

 ropodia ; there is also a longitudinal groove middorsally through the first 

 7 setigerous segments. The ventrum is neatly biannulate and the rings 

 are smooth. 



Separation between the thorax and abdomen is externally unmarked 

 except for the change in parapodia of setae to hooks. Lateral organs, 

 present from the first thoracic setigerous segment, are small, partly retrac- 

 ted papillae in the short, transverse groove between notopodia and neuro- 

 podia but nearer the former; they are continued posteriorly but are 

 nowhere conspicuous. Nephridial pores, also inconspicuous, are present 

 in intersegmental grooves nearer the dorsal side; the first are present 

 between setigerous segments 11 and 12; they are continued posteriorly 

 through at least the first few abdominal segments. They are not clearly 

 marked, perhaps because none of the individuals seem to be mature; 

 genital apertures have not been distinguished, possibly for the same 

 reason. 



Branchiae are retracted on all parapodia except a few in one indi- 

 vidual but their approximate distribution can be determined by the pres- 

 ence of a small pore at the superior edge on median and posterior 

 abdominal segment and they are continued posteriorly through a long 

 region. 



Uncinal ridges are provided with many hooks in a row, as originally 

 described. The hooks are similar to one another throughout. Their inter- 

 esting details have been worked out based on neuropodia from a median 

 region but others have been checked for the same details and found to 

 agree. The most conspicuous feature is the nearly complete coalescence 

 of the 3 teeth in the crest so that they can be hardly distinguished unless 

 sharp focus is brought to bear on their tips (pi. 56, fig. 2) ; otherwise the 

 crest resembles a heavy transverse ridge elevated above the fang. The 

 hood is short but spacious (pi. 56, fig. 1) and has a finely serrated edge. 

 The node is abrupt but shoulder and neck are less developed than in other 

 species of Dasybranchus (compare pi. 56, figs. 1, 3; pi. 57, fig. 2). 



D. lunulatus inhabits muddy sand shoals in marine or estuarine 

 localities. In life it is deep blood red. It autotomizes readily. 



The collections listed above were obtained through the courtesy of 

 the directors of the Bass Biological Laboratory, Englewood, Florida, and 

 the U. S. Fisheries Laboratory, Fivers Island, Beaufort, North Carolina 



