1909.] NATURAL SCIENCES OF PHILADELPHIA. 263 



Pygidium a short tube with large terminal anus surrounded by a 

 membrane bearing a circle of minute papillae and a small but distinct 

 pair of ventral cirri knobbed at the ends. 



Parapodia begin on II. When fully developed at about X the 

 neuropodia consist of low fleshy projections at the extreme dorsal level 

 of the sides; they bear a scarcely evident presetal lobe and a more 

 prominent thick postsetal lobe which rises above into a free process 

 especially evident on the more restricted neuropodia of anterior and 

 posterior segments. Setae are of a deep brown color and form a con- 

 spicuous palisade of five or sometimes six vertical series arranged 

 in an elliptical area three times as deep (dorso-ventrally) as long 

 (antero-posteriorly) on middle segments, but less deep anteriorly 

 and posteriorly. In the posterior region neuropodia become reduced 

 to small pointed processes situated ventro-laterad of the notopodia, 

 with which they are united by an integumental fold ; they bear a tuft 

 of inconspicuous setae. Notopodia of anterior region dorsal, separated 

 from the neuropodia by a short interval and consisting of a short setig- 

 erous tubercle and a small but prominent postsetal lobe thickened 

 along the lateral border and rising mesially into a pointed process; 

 they bear small spreading tufts of setae of various lengths, the longest 

 directed mesially. Except that they become more elevated, the post- 

 setal lobes erect and sublanceolate in form and the setae reduced to 

 small vertical fascicles, the notopodia are little changed in the posterior 

 region. 



Branchiae appear at from VII to X as slender and inconspicuous pro- 

 cesses as long as the segment and arising from the dorsum just mediad 

 of the notopodia. No marked change is undergone until, passing 

 into the posterior region at about XXIX, they abruptly become much 

 longer, flattened and lanceolate, densely ciliated on both borders and 

 united to the notopodia by a membranous fold. They completely 

 fill the dorsal field between the notopodia and generally extend mediad 

 until they touch and bend sharply dorsad. They continue to the 

 posterior end. 



No clear distinction between acicula and setae exists, but some of 

 the latter reach deeply into the body walls and serve for muscular 

 attachment. On typical anterior neuropodia the stout, brown setae 

 form a conspicuous palisade of five (or rarely six) vertical rows which 

 bend backward and successively overlap. Those of the posterior 

 series (PI. VIII, fig. 34) are stouter than the others, with short, blunt 

 roughened tips; the others (fig. 35) are abruptly contracted imme- 

 diately beyond the surface of the body and taper into long, acute tips 



