1923] NATURAL SCIENCES OF PHILADELPHIA 211 



Remaining thoracic segments obscurely defined, very smooth 

 above, very obscurely aimulated ventrally, with rather poorly 

 developed glandular transverse bands or ridges. A small s])ecimen 

 which is strongly contracted has the segments ])etter defined. 

 Abdominal segments similar but separated by more distinct furrows, 

 tapered and decreasing in length caudally. 



Gills arranged much as in other species, in converging oblique 

 lines, but the first pair crowded somewhat outside of the second 

 pair on the dorsum of VI, and those of the last pair very nearly 

 in contact on the dorsum of V, but as usual connected with the 

 parapodial region of VI by a ridge. Interbranchial field broad 

 but short, being confined to III and IV. There is no free inter- 

 branchial fold, this region being connate with III to form the 

 tumid region referred to above. Gills delicate, long and slender, 

 tapered, with sub-filamentous ends, subequal, generally about two 

 and one-half times width of body, the last reaching to XII on the 

 type and to XVI on a smaller specimen. 



Pygidium a very short ring with large subpentagonal anus and 

 one pair of short, thick conical, papilliform cirri. 



The first parapodium on IV (Plate XVll, fig. 19) has a discoid 

 flattened end supported on a slender foot and lies at a more ventral 

 level than usual in the genus. The parapodium on V (Plate XVII, fig. 

 20) is larger, slightly dorsal to the succeeding ones, flattened and 

 of an almost sigmoid form owing to the addition to its enlarged, 

 ventrally hooked end of a small wing on the ventral aspect of the 

 base. Parapodium VI (Plate XVII, fig. 21) is somewhat flattened 

 and bears a slight ventral wing, but no enlarged hooked end and is 

 consequently nearly normal in form. Remaining thoracic parapodia 

 are biramal and except for the relatively smaller size of both the 

 setigerous tubercles and the uncinigerous tori are quite similar to 

 those of A. anops. Posterior tubercles bear no ventral papillce. 

 Largest tori on middle thoracic segments are from ^ to l, the 

 body width on different specimens. 



Abdominal parapodia (Plate XVll, fig. 22) consist of small thick 

 tori situated at the extreme ventral level of the bodj^ bearing small 

 papilliform cirri at the dorsal end of the uncinial series and, widely 

 separated from these near the dorsal level, the dorsal cirri with 

 flattened ovoid ends hooked ventrally and supported on short, 

 slender bases. 



Setse begin on IV; the fascicles on IV and V much reduced, only 

 the extreme tips of the fibroid seta) appearing from a minute pore 

 on the anterior face of the parapodium far proximad of the end 

 of the tubercle. On VI, the fascicle is larger and more normal, the 

 setse appearing between the short terminal lips of the tubercle. 

 Other thoracic fascicles conspicuous, folded into a trough-like 

 form and composed in the usual manner of 12-15 pairs of large 

 and small acute limbate setae. 



