NEREIS (CERATONEREIS) ALASKENSIS, A NEW POLY- 

 CHAETOUS ANNELID FROM ALASKA. 



By A. L. Treadwell, 



Of the Department of Zoology, Vassar College, Poughkeepsie, New York. 



Among the recent annelid accessions of the United States National 

 Museum submitted to me for identification is an apparently unde- 

 scribed polychaete. The single specimen was taken by Lieutenant 

 Colonel C. A. Seoane, Signal Corps, United States Army, from 

 the cable in Valdez Harbor, Alaska, which was brought aboard the 

 United States Army Tender Bumside during repairs to the cable in 

 December, 1920. The depth at this point was given as 200 fathoms. 



NEREIS (CERATONEREIS) ALASKENSIS, new species. 



Type specimen.— C2ii. No. 19029, U. S. N. M.; Valdez Harbor, 

 Alaska, in 200 fathoms. 



Description. — Apparently much distorted anteriorly by crowd- 

 ing into the bottle used for preservation, the prostomium with its 

 appendages has been flattened against the anterior end of the peri- 

 stomium so that its original form is diflBcult to determine. 



The sides of the anterior half of the prostomium are nearly paral- 

 lel to one another, the anterior half being narrower than the posterior. 

 The tentacles are in contact at their bases and are about half as long 

 as the prostomium. The posterior half of the prostomium is about 

 twice as wide as the anterior, and has two pairs of very prominent 

 dark eyes with large lenses. The palps are very prominent, attached 

 to the prostomium for the greater part of its length. In the present 

 condition of the specimen, the terminal joints of the palps are with- 

 drawn into the basal portion, so that the latter has a truncated ap- 

 pearance. 



On the right side the only tentacular cirri present are the two of 

 the anterior pair and the ventral one of the posterior, while on the 

 left only the two ventral ones remain. All are much shriveled, the 

 longest, the dorsal one of the anterior pair on the right side, extending 

 as far as somite 5. The anterior somites seem to be much contracted, 

 so that it is probable that in the living individuals these cirri would 

 not reach so far. Somite 2 is about one-third shorter than 1, which 



No. 2397.— Proceedings U. S. National Museum. Vol. 60, Art. 2. 

 3136— 22— Proc.N.M.Vol.60 5 1 



