230 PROCEEDINGS OF THE ACADEMY OF [April, 



XIV, which is exactly at the middle of the body, is the longest; but 

 the reduction in l^oth length and diameter of the segments is slight until 

 near the ends, where it becomes more rapid. The pygidium is a short 

 squarely truncated tube marked externally by longitudinal grooves 

 which correspond with the clefts between the nine to twelve uneven 

 lobes into which its margin is divided. 



The surface of the body is vesiculated or finely pustular in the follow- 

 ing manner: Generally over the posterior half of the body, in all of 

 the intersequental furrows and on all except the most anterior setig- 

 erous areas, the pustules are very small and, though numerous, not 

 crowded. In macerated specimens they are collapsed and appear 

 as punctations. From the middle of the body they gradually increase 

 in size forward. Each annulus of anterior somites is provided on its 

 highest part with an irregular transverse series of very large vesicles 

 which usually lie nearer to the posterior margin and overlap the suc- 

 ceeding ring, when the worm is contracted, as a rough and irregular 

 fold interrupted in the median dorsal region. These folds and their 

 vesicles are usually best marked on the middle ring of each somite, on 

 which they increase in prominence from the median break laterally 

 to the setigerous areas, below and even more above which they form 

 rough lobes overlapping the third ring. The ventral lobe bears the 

 ventral sensory pit referred to above. Anteriorly the transverse series 

 of enlarged vesicles tends to form several rows and all of the vesicles to 

 increase in size. The first three segments bounding and anterior to the 

 mouth are covered nearly uniformly with vesicles of moderate size; 

 and similar ones cover the anterior two-thirds of the setigerous areas 

 of the first ten or twelve segments. The prostomium is perfectly 

 smooth and lacks surface vesicles altogether. Posteriorly the ridges 

 of enlarged vesicles and the lateral lappets become gradually flattened 

 out and the entire surface much smoother. The lappets above and 

 below the setigerous areas remain, however, and may become even 

 more prominent on the last few segments, where, however, they are not 

 vesicular. 



Neuropodial cirri appear on III and continue on every segment to 

 near the posterior end, ceasing on from XXIV to XXVII in different 

 specimens. They arise at the dorsal margin of the setigerous area, 

 chiefly from the third annulus but in part from the second also. At the 

 base their diameter nearly equals the length of the third annulus, but 

 they quickly become slender. The surface is strongly wrinkled trans- 

 versely, much like the contracted tentacle of a jelly-fish, and doubtless 

 they are in life capable of great extension;, but in the preserved speci- 



