ONUPHIS PROALOPUS. . 2G7 



convex tlu'oughout. Most somites, excepting the first few, are a little depressed 

 along the middorsal line and also along the midventral line. Intersegmental 

 furrows deep and distinct. The first and second metastomial somites are about 

 equal in length, which is nearly the same as that of the prostomium, and are 

 about three times as wide across the anterior end as long. The third metastomial 

 somite is shorter in about the ratio eleven to thu'teen. It shows a distinct 

 transverse sulcus, there being only a weak transverse depression on the first two. 

 The succeeding somites do not show a distinct transverse sulcus. They gradu- 

 ally decrease in length to the seventh, which is between five and six times wider 

 than long and which is scarcely more than half as long as the first metastomial. 

 The following somites maintain practically this same actual length thi-oughout 

 most of the fragment, the most caudal ones, however, being shorter in about the 

 ratio of five to seven. 



The first parapodia are cylindrical and very long, and extend almost di- 

 rectly forward along the sides of the peristomium and prostomium beyond the 

 middle of the latter and very nearly to its anterior end, the cirri projecting 

 beyond the anterior end. The notocirrus is attached above, a little proximad 

 of the middle, has a narrowed cirrophore, just above which it is moderately 

 thickened, and then tapers to a point. The neurocirrus, attached on the ventral 

 side, and nearly opposite to the notocirrus, is similar in form, but is smaller. 

 There is only a slight presetal elevation, whereas there is a tapered, cirrus-like, 

 postsetal process as long as the neurocirrus. (Plate 41, fig. 3). The succeeding 

 five pairs of parapodia are smiilarly attached to the anterior border of their 

 somites but project less directly cephalad and are shorter though still compara- 

 tively long. (Plate 41, fig. 4). Beginning with the sixth, the parapodia, now- 

 attached at middle of length of somite, extend more ectad, at the eighth directly 

 so, at the same time becoming greatly shortened. (Plate 41, fig. 4). At the same 

 time they are shifted dorsad and at the eleventh attain the dorsal level which is 

 maintamed thereafter. Caudad the postsetal process gradually becomes shorter, 

 appearing only as a short, thin lobe and finally quite absent caudad of the eight- 

 eenth parapodia. The notocirri in the most anterior parapodia are long and 

 slenderly tapering, reaching to or shghtly beyond the middorsal line. They 

 continue to be prominent on all parapodia, but posteriorly they become ex- 

 tremely slender and filamentous while maintaining the same or nearly the same 

 length. The neurocirri are well-developed, tapering processes on the first seven 

 pairs of parapodia. Beginning with the eighth parapodia they are reduced to 

 flattened scutes merging in the glandular area. 



