PLATYNEREIS POLYSCALMA. 221 



one and contiguously to it. It is stouter than the ventral one and reaches to 

 the eighth or ninth somite. The ceratophore is short and cylindrical, is usually 

 as thick or nearly as thick as the style at the base of the latter, and is annulate. 

 The style is strongly varicose or irregularly jointed. The ventral cirrus of the 

 posterior pair is attached just caudad and a little dorsad of the base of the 

 anterior dorsal. The style is swollen toward the ceratophore, running out distad 

 to a slender tip and reaching caudad to the fifth to seventh somite. The pos- 

 terior dorsal tentacular cirri are broken off in all the types, but judging from 

 the basal portions, they must be somewhere near the size of the anterior dorsals. 

 Each is attached just above the corresponding ventral one. (Plate 31, fig. 2). 



The setigerous somites are all very short. They are arched but moder- 

 ately and about equally above and below, the body in general being somewhat 

 lenticular in cross-section with the ventral arch a little flattened. Dorsally 

 the somites are entire and are crossed longitudinally by well-separated striae 

 over the entire arch. Ventrally a longitudinal neural band is set off by furrows, 

 laterad of each of which on each somite of the anterior division there is a trans- 

 verse sulcus extending toward base of parapodium and thus bisecting the somite, 

 though these sulci are not uniform. There are also some light longitudinal 

 striae. The pygidium is very small, subtrapeziform in outline, with the two cirri 

 small and subcorneal. 



In the nereid division of the body there are two groups of parapodia sharply 

 distinguished by the character of the notocirri, the eighth and succeeding para- 

 podia having notocirri abruptly much smaller and different in shape from those 

 preceding. The notocirrus of the first parapodium has a short, thick cirrophore 

 with the style thick, swollen at base, above which it presents a long, much more 

 slender, angularly bent part which is distally flattened and on one side of the 

 end presents a short angular process. In the second parapodia the style of the 

 notocirrus is distally much broader and the terminal extension is larger. In 

 succeeding parapodia the notocirri increase in length and expand more and 

 more distally, the style being flattened and enlarging clavately distad, the 

 distal expansion presenting from its distocaudal angle an acutely pointed process 

 projecting caudad or ventrocaudad and appearing like the beak of a bird from 

 its head. In the seventh parapodia the notocirri project distinctly beyond the 

 tips of the setae. (Plate 31, fig. 5). On the eighth parapodia the notocirrus is 

 abruptly much shorter, with the style cylindroconical in form and not attaining 

 the ends of the shafts of the setae. (Plate 31, fig. 6). On succeeding parapodia 

 to the end of the nereid division the notocirri decrease progressively in length. 



