504 PROCEEDINGS OF THE ACADEMY OF [NoV., 



forward from and between the posterior tori to an apex halfway to the 

 tori of IX, whence a narrow median ventral ridge continues it forward 

 to the glandular zone of IX; XI and XII have no glandular areas, 

 though the tori form prominent swellings near their posterior ends. 



The posterior segments are much contracted and distorted, but it is 

 evident that they consist normally of a slender, very contractile, and 

 wrinkled anterior portion, and a short, enlarged, posterior parapodial 

 portion. They decrease in length regularly to the pygidium, which is 

 preceded by three achsetous segments, of w^hich the fu'st closely re- 

 sembles the last setigerous in size, and has posterior swellings repre- 

 senting the parapodia ; the next is about one-half and the next one- 

 fourth as long, widest posteriorly, where there are slight parapodial 

 thickenings. The last two gradually widen into the base of the 

 pygidium. 



Pygidium (Plate XIX, fig. 8) with a short basal ring resembling the 

 last achffitous segment, and bearing a thick posterior anal disk, the 

 margin of which is provided with a median ventral cirrus and a pair of 

 lateral, long, slender cirri each having a length of f the diameter of the 

 disk, together with a circle of very regular prominent teeth of which five 

 are between the median and each of the lateral cirri, and fifteen between 

 the two latter on the dorsum. Anus occupying the centre of a low, regu- 

 lar, finely furrowed cone, and closed by a thick, fleshy papilla, which 

 arises from its ventral margin and bends dorsad. The usual raised nem-al 

 line runs for the entire length and passes on to the ventral cirrus, 



Setse and uncini are undeveloped on the regenerating segments. 

 They are sessile on VI-IX and borne on small papillae and promi- 

 nent tori on all the others. Anteriorly the seta form small but very 

 prominent, vertical, linear tufts, which become more compact pos- 

 teriorly. They are similar on all segments. Anterior tufts contain 

 10-12 longer, stouter, slightly curved, narrowly limbate setse (fig. 9), 

 with long, capillary tips, and nearly twice as many slender, capillary, 

 wingless setse, partly smooth and partly bipinnate, with fine hairs 

 (fig. 10), Farther back they become longer but fewer and in more 

 compact bundles, and most of the wingless setse are smooth. 



The anterior thoracic crochets are of course unknown. On other 

 segments there are 15-19, the larger numbers behind. They are pale 

 yellow, strongly striated, with rather slender stem, slightly con- 

 stricted to form a neck, but lacking a distinct shoulder; an expanded 

 head with a short, stout beak; a low crest with about four large and 

 two or three small, diminishing teeth flanked by small fibrous teeth; 

 and a conspicuous guard composed of 5-6 stout flattened hairs united 



