846 PROCEEDINGS OF THE ACADEMY OF [DcC, 



NEW SPECIES OF AMPHARETID^ AND TEREBELLIDiE FROM THE 

 NORTH PACIFIC. 



BY J. PERCY MOORE. 



Among the Polychseta dredged by the steamer Albatross while in the 

 service of the Alaskan Salmon Commission of 1903 occur the following 

 new species. Two previous papers based upon the same collections 

 have been published in these Proceedings for 1905. 



AmpMcteis alaskensis sp. nov. (Plate XLIV, figs. 1-4.) 



The available examples of this species vary in length from 22 to 76 

 mm. One selected for the type is 33 mm. long, of which the thorax is 

 19 mm.; its greatest width is 4.3 mm., and the cephalic cone is 2.3 mm. 

 in both length and breadth. 



Counting the region of trunk anterior to the paleoli as formed of 

 two somites, the worm consists of thirty-four segments and the py- 

 gidium. The setigerous segments are from III to XX inclusive, and the 

 uncinigerous VII to XXXV inclusive. 



The median prostomial plate (fig. 1) is shield-shaped, about twice as 

 long as broad, the posterior end pointed, the anterior cleft in the middle 

 and formed of two somewhat divergent lobes. On each side of, the 

 plate is a broad, low, lateral ridge broadly rounded anteriorly and reach- 

 ing not quite so far forward as the median plate. Bounding both these 

 ridges and the plate posteriorly is a pair of transverse folds curving 

 slightly forward laterally and caudad medially to meet in the median 

 line at a sharp angle. These ridges are pigmented with brown above and 

 they form the angle at which the nearly vertical anterior portion of the 

 prostomium meets the nearly horizontal posterior region. The latter 

 is much broader than the former and at its convex posterior margin 

 nearly twice as wide as long. All of these parts taken together consti- 

 tute the dorsal face of the prostomium. Beneath, and usually retracted 

 within the mouth, is the folded tentacular membrane bearing a few 

 short slender tentacles which scarcely exceed the cephalic cone in 

 length. The somewhat quadrate prostomium is bounded by the short 

 peristomial ring which completes the base of the cephalic cone. 



The large mouth is bounded below by the prominent thickened peris- 

 tomial lip, while dorsally the peristomium is much shorter and over- 



