ONUPHIS PACHYTMEMA. 281 



but is decidedly shorter than the first two together. Each of the first three 

 metastomial somites is widest across the anterior end at the level of attachment 

 of parapodia, narrowing to the caudal end. The length in these is about three 

 fifths the greatest width. They are only obscurely marked off from each other 

 dorsally. The third is separated from the fourth by a sulcus more distinct than 

 that between those either in front or immediately caudad. The somites of the 

 posterior median and caudal portions of the body are very distinctly separated 

 above as well as laterally and ventrally. The fourth somite is much shorter 

 and is two and a half times wider than long. From here caudad the somites 

 increase in width to near the tenth, thereafter remaining more nearly uniform 

 to the caudal region. The somites near the tenth are twice or a little more 

 as wide as long. In this region they are decidedly flattened dorsoventrally, the 

 dorsum being but weakly arched and the venter flat. The dorsum is some- 

 what more highly arched again in the posterior median region. The somites 

 present the usual whitish, transversely elongate, swollen glandular areas below 

 the parapodia. 



The parapodia of the first three pairs are moderately prominent and project 

 obliquely forward. They are attached at the anterior border of their respective 

 somites near the ventral level. With somite V (fourth pair) they begin to be 

 shifted dorsad, and at somite IX they have attained the dorsal level and at the 

 same time have had the bases shifted back from the anterior border and are 

 greatly shortened. The fourth parapodia project less strongly forwards and 

 the succeeding ones extend out nearly horizontally. The first parapodia are 

 stout. Each bears a notocirrus attached near the middle dorsally, a neuro- 

 cirrus attached farther proximad on the ventral surface, and is distally extended 

 into the setigerous neuropodial lobe which presents a conspicuous, cirriform, 

 postsetal process. The notocirrus is slenderly tapered from the base as usual; 

 it reaches less than halfway to the middorsal line; the cirrophore is low. The 

 neurocirrus is similar in form to the notocirrus, but is somewhat shorter. The 

 postsetal process does not extend out quite to the level of the tip of the noto- 

 cirrus. (Plate 48, fig. 5) . In succeeding parapodia the notocirri continue to the 

 last, but decrease gradually in length and become much more slender, with the 

 base in the anterior ones more constricted. The neurocirrus is much shorter 

 on the second parapodia and on the third is but a rather short, conical body; 

 on the fourth parapodia it is reduced to a low, rounded prominence and on suc- 

 ceeding somites it is a simple plate merged with the glandular swelling. The 

 postsetal process is much reduced on the second and third parapodia and by the 



