1906.] NATURAL SCIENCES OF PHILADELPHIA. 355 



and marked only by the small transverse muscle bundles, apparently 



4 to each segment. 



If perfect, as it appears to be, the pygidium presents striking char- 

 acteristics. The large median spoon-shaped lobe of A. aulogaster is 

 absent and represented only by a minute slender process. The 

 lateral lobes are much larger, obliquely truncated above, and slightly 

 indented at the end. 



The parapodia arise from the dorso-lateral surface of the lateral 

 muscle bands and are about equally well developed throughout. 

 They form small but distinct bluntly rounded tubercles produced 

 into a small, conical prominence and apparently unsupported by an 

 aciculum. They bear only a small ventral cirrus and a prominent 

 dorsal branchia, the small dorsal cirrus which has been figured for 

 some species being absent. Branchise are absent from the first pair 

 of parapodia, but are present on all of the others. They are largest 

 on the middle segments, where they exceed a millimeter in length and 

 the parapodium in diameter. They are slender and slightty tapering in 

 form and provided along one side with a strongly developed longitudi- 

 nal muscle, rendering them very contractile. 



The setae are all simple, colorless, tapering, capillary bristles, longi- 

 tudinally fibrillated and soft in texture. They are arranged in two 

 fascicles, a dorsal of 6 to 10 setse which reach f the length of the 

 branchia, from the base of which they arise, and a ventral which arises 

 from beneath the conical prolongation of the parapodium and contains 



5 or 6 setae less than h as long as the dorsal bristles. 



Along the sides of the body between the parapodia, but nearest to the 

 succeeding one, are small black or dark brown and very conspicuous 

 eye spots, which are hemispherical in shape and indistinctly facetted on 

 the surface. 



The only specimen, a female filled with eggs, is No. 284 of the Acad- 

 emy's collection, taken by Dr. Benjamin Sharp at Icy Cape, Alaska, 

 on August 17, 1895. 



