208 PROCEEDINGS OF THE ACADEMY OF [Vol. LXXV 



bearing tubercles but without paleoli at the sides and forming a 

 thickened and somewhat elevated, but little free, prebranchial 

 fold above, the middle part of which is continued caudad over 

 segments IV and V. 



The next three segments are podous and branchiferous. Dorsally 

 they are annulated and each bears a prominent transverse glandular 

 ridge covering most of its surface. The branchial scars are borne 

 on the medial ends of tumid areas so arranged that they converge 

 in a pair of slightly oblique lines, the posterior and most approxi- 

 mate ends being separated by about one-third of the body width. 

 The first two pairs of scars are on IV, the third and fourth pairs 

 on V, though the last is connected with and really belongs to VI. 

 Remaining thoracic somites are larger, the maximum ratio of 

 length to width being about 1.2. Dorsally they are strongly 

 arched, smooth and rather soft, divided into three or six rings. 

 Ventrally the parapodial annulus is largely occupied by a glandular 

 plate which rises to a prominent ridge on the first two or three 

 uncinigerous segments and then becomes gradually flatter. On 

 the last few thoracic segments the glandular plate is much reduced. 



Branchiae very easily detached from the small scars and on these 

 specimens seldom found in place. They differ much in size in the 

 several specimens and it is evident that normally they are fre- 

 quently lost and regenerated. The type bears three partly grown 

 ones in place. When full grown the gills are large, thick, tumid 

 at the base, and taper gradually to slender tips; length about 

 twice the maximum diameter of the worm or two-fifths the length 

 of the thorax. For most of their length they are ridged longitudi- 

 nally and marked with cross furrows, which together with the 

 fact that they are twisted into a spiral, gives them a striking re- 

 semblance to the figure of a ram's horn. 



The thorax passes regularly into the abdomen, the segments 

 differing only in the character of the parapodia and the abseiice 

 of ventral glandular plates on the abdomen. Abdomen short, 

 one-half or less the length of the thorax and consisting of eleven 

 segments, the anterior six of which taper rapidly to a groove 

 behind which the remaining five are of nearly uniform width but 

 progressively more depressed. The last two or three are short and 

 much crowded. 



Pygidium a very short ring with large open anus bounded by 

 a ventro-lateral pair of short, stiff, thick styles above which are 

 four or five small papillae or crenulations on each side. 



Parapodia begin on IV, I to III being entirely apodous. On 

 somites IV-VI (Plate XVII, figs. 14, 15) they are small tubercles 

 with enlarged and somewhat flattened ends and vestigial setae which 

 on the first two apparently quite fail to reach the surface and on 

 the third barely project. Remaining thoracic segments (VII- 

 XVIII) bear both setigerous tubercles and uncinigerous tori. 



