EEEANTIATE POLYCHAETA OF JAPAN. 177 



Nereis shishidoi n. sp. 

 PI. XIX, figs. 10—18. 



Body stout, consisting of 121 segments, 180mm. long; 

 its breadth 10 mm. without, and 14 mm. with, parapodia and 

 bristles in the broadest region of body, i.e., at about lOtli 

 segment. 



Prostomium longer than broad (fig. 10), tentacles J as long, 

 separated at base and divergent. Palpi large, closely appressed 

 to tentacles, the terminal bosses reaching almost to tip of 

 tentacles. Posterior pair of eyes lies close to the posterior 

 border of prostomium ; anterior pair at a little distance from 

 the posterior pair, the two eyes being more apart from each 

 other. 



Peristomium (figs. 10, 11) forming a collar as in Nereis 

 cyclurus Hapjngtox, to which tliis species comes nearest ; longer 

 tlian the two succeeding segments taken together on the dorsal 

 side, and as long as the leiigtli of the 4 succeeding segments on 

 the lateral side ; smooth above, but ventrally and laterally with 

 longitudinal wrinkles. Tentacular cirri small, the longest reaching 

 to 4tli and the shortest to ord segment. 



In the first parapodium (fig. 12), dorsal cirrus is almost 

 twice as long as the superior ligula, which has an elongated coni- 

 c;d outhne ; the ventral cirnis ratlier stout, slightly longer than J 

 tlu- di'i-snl ; only one acicula present. 



In the lOtii parapodium (fig. 13), superior ligula is enlarged 

 to a lieart-sliaped flap ; the dorsal cirrus arises from the dorsal 

 border of the latter near the base of parapodium and is shorter 

 than same of the 1st parapodium; middle ligula well developed. 



