548 PROCEEDINGS OF THE ACADEMY OF [-IuIVj 



neuropoclium divides distally into presetal and postsetal lobes, of which 

 the former is short and broadly rounded and without any appendage 

 to about XX, wdien a small papilla appears projecting freely from its 

 anterior and distal margin directly outward or slightly ventrad. This 

 increases in size for several somites, but becomes again greatly reduced 

 by XLV. The postsetal lobe is always much more prominent ; on the 

 first few somites it is rather narrowly foliaceous and strongly curved 

 dorsad, ending in a blunt apex; by somite IX it has become much 

 broader, fully equals in length the base of the parapodium and bears a 

 small but distinct branchial process on the dorsal border near the end. 

 From this point the branchial process increases rapidly in length and 

 becomes somewhat broad and flattened, while the postsetal lobe itself 

 becomes gradually wider (deeper) and shorter, until by XXII it no 

 longer reaches beyond the presetal lobe. At this point the branchial 

 process fully equals the rest of the parapodium in length and projects 

 prominently directly upward. Both the foliaceous margin of the post- 

 setal lobe and its process have an open structure and are richly vascular 

 and they undoubtedly serve as gills. Posterior to XLV the branchiae 

 are so reduced that the foot (fig. 40) consists only of a tapering base 

 bearing small conical divergent presetal and postsetal lobes which 

 become still further reduced toward the caudal end. 



Anteriorly each parapodium is supported by three black aciculse 

 which are curved and tapered distally and terminate in an acute pale- 

 colorecl tip projecting freely beyond the surface. Posterior parapodia 

 have but two (fig. 41) . The setre are of two forms, one winged and with 

 acute tips, the other hooded crochets. The former (fig. 42) have black 

 bases and pale yellow exposed portions, are sigmoidly curved, provided 

 with a delicate wing and taper to very acute tips. They vary some- 

 what in length, curvatiu'e and extent of the border. The crochets (fig. 

 43) are black or deep brown throughout, strongly striated, very slightly 

 enlarged distally and then contracted to a scarcely hooked tip provided 

 with five teeth, of which the lowermost greatly exceeds the others in size. 

 The hood consists of the usual pair of delicate striated pieces which 

 embrace the end of the crochet and conform to its shape. Most of 

 the setse are broken, but enough can be made out of a comparison of all 

 the specimens to show that acute setee alone, to the number of about 

 12 or 14 arranged in a fan-shaped fascicle, are found in the anterior 

 parapodia. The number gradually diminishes and about the middle of 

 the branchial region crochets appear and continue in association with 

 the acute setse throughout the middle region, while posteriorly 3 or 4 

 crochets alone remain. 



