720 PROCEEDINGS OF THE ACADEMY OF [Nov., 



DESCRIPTIONS OF TWO NEW SPECIES OF POLYCH^TA FROM WOOD'S 

 HOLE, MASSACHUSETTS. 



BY J. PERCY MOORE. 



Nereis arenaceodentata n. sp. 



A small, slender species, seldom exceeding an inch in length. The 

 head (PL XL, fig. 1) is about as long as broad, roughly quadrate, 

 with the posterior side about l{r times the anterior, which is strongly 

 conyex, the lateral borders bulging posteriorly, excayated and wrinkled 

 anteriorly. The two pairs of conspicuous, black, broadly elliptical 

 eyes are almost in contact near the postero-lateral angles of the head ; 

 the anterior somewhat more widely separated and slightly the larger. 

 Frontal tentacles about f head, slender, conical, di\'ergent; their bases 

 separated by about twice their diameter. Palps thick, swollen at the 

 base, conical but suddenly constricted and bent at the terminal third ; 

 the style minute and retracted but reaching beyond the frontal tenta- 

 cles. Tentacular cirri all relatively short and moderately slender, with 

 yery short crowded basal pieces; the anterior dorsal is about equal to 

 the head ; the anterior yentral about f , the posterior dorsal about 

 twdce and the posterior yentral about f as long. The buccal region is 

 swollen and wrinkled. 



At the anterior end a region of the body comprising the first 4 or 5 

 somites is considerably enlarged and quite terete ; the body then rap- 

 idly narrows to about somite X, beyond which it is nearly linear and 

 of uniform diameter to near the caudal end. At first the parapodia 

 are small, Init increase in length as the width of the body diminishes, 

 so that the total wddth remains nearly uniform. Beyond the first 

 third the length of the parapodia equals the width of the body and the 

 animal assumes a depressed aspect. The caudal end terminates quite 

 abruptly in a short pygidium bearing a pair of anal styles equal in 

 length to the last 8 or 9 segments. There are 49 setigerous somites 

 in the type. 



The parajjodia are all distinctly biramous. In the first (fig. 2) tlie 

 notopodium is relatiyely small and simple and is achsetous and lacks 

 an aciculum; it consists of a short cylindrical base bearing a single 

 conical lobe, and an equally long, but more slender, dorsal cirrus. 

 The neuropodium is larger, contains an aciculum and bears setae; 



