170 PROCEEDINGS OF THE ACADEMY OF [Jan., 



into an inner and an outer series, the barbs of wliich face each other. 

 The radioles are thick and short, with a short, thick, finger-hke termi- 

 nation lacking barbs, and in one specimen, not enclosed in a t\ibe, are 

 curled inward at the ends. There are no branchial eyes. Except near 

 the end, where they become shorter, the barbs have a length of about 

 f the diameter of the thorax and are numerous and crowded. Three 

 or four of the dorsalmost radioles each bear at the base a larger barb, 

 about 3 times as thick as the ordinary ones and somewhat longer. 

 Near the median line and at a somewhat more dorsal level is the pair 

 of tentacles of similar form but somewhat stouter. A membranous 

 fold encircles the base of the gills within and surrounds the mouth. 

 The last three features were clearly made out on the incomplete 

 specimen only, not on the type. 



The operculum (figs. 21, 21a) is dorsal antl dextral. It has a slender, 

 ■wi'inkled, somewhat flattened stalk very slightly broader at the distal 

 end and without wings or membranous margins. The body of the 

 operculum is broadly egg-shaped, the basal f with soft non-chitinous 

 walls somewhat longitudinally folded, the distal f a smooth, bro\An 

 and firm chitinous dome with a narrow thickened double ring at the 

 base and the surface with traces of a rough calcareous incrustation. 

 In the type the stalk measures 4 mm. in length, .7 mm. in diameter, 

 and the body is 2.5 mm. long and 2 mm. thick. On the larger 

 specimen these measurements are respectively 4.5, .7, 2.5 and 2 mm. 



On the type the collar and thoracic membrane are closely folded 

 about the body from contact with the tube, but evidently fully agree 

 with the following description, based on their expanded state in the 

 larger cotype. The collar is produced directly forward for a distance 

 of 1 mm. from the prostomium for the entire width of the space be- 

 tween the ventral margins of the setigerous tubercles. At the sides 

 short round lobes are produced, but there are no other processes and 

 no clefts. The thoracic membrane extends as a broad modulating 

 fold from the first to the fifth torus inclusive, overlapping its fellow 

 medially, the lateral margin of the collar anteriorly, and the sixth torus 

 caudally. 



The first setigerous tubercle is included in the base of the thoracic 

 membrane; the others form, with the uncinigerous tori, freely project- 

 ing flaps which increase in size and prominence from the second cau- 

 dally, the last being especially large, nearly twice its predecessor, and 

 almost reaching the median line ventrally, while dorsally it partly 

 covers and conceals the, in this case, detached setae tuft. The body is 

 slightly flattened and tapers to the caudal end, where the nearly 



