406 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
latter case incurved over the dorsum, in the former extending 
nearly at right angles to longitudinal axis of the body. 
Digestive system exhibits a well-developed trepan (Fig. 73) of 
ten teeth ; these are surrounded by a circlet of elongated papillae 
{pop.). Oesophagus of moderate length (extending through 22 
somites), strongly chitinized ; proventriculus cylindrical, of uniform 
diameter throughout; two well-defined lateral raphes ; radial muscle- 
columns very large. Alimentary canal back of proventriculus with 
extensive, segmental, paired diverticula. 
Dorsetl surface elegantly marked with fine transverse dark lines 
which indicate the boundaries of the segments. 
Posterior extremity capable of producing successive crops of col¬ 
lateral, sexual buds or zooids (Fig. 76), which possess every exter¬ 
nal structure of the parent except mouth and anus. They lack, 
however, an alimentary canal and nephridia. 
Length , 68 mm.; transverse diameter, 3 mm.; dorso-ventral 
diameter, 1 him. 
A single specimen was collected by the Columbia University 
expedition, probably in the vicinity of Port Townsend. Unfor¬ 
tunately, no data accompany it. This individual possesses the 
remarkable sexual zooids, over fifty in number, presenting all 
stages of development. They arise as collateral buds from a prolif¬ 
erating somite near the posterior extremity (Fig. 76). At full 
maturity they evidently separate from the asexual stock and become 
free-swimming sexual zooids, provided with parapodia, antennae, 
eyes, and central nervous system, but destitute of an alimentary 
canal. They will be fully described in volume 2 of the Biological 
Bulletin. 
OxUPHIDIDAE. 
22. Northia elegans sp. nov. PI. 8, figs. 77-85. 
Form stout, flattened dorso-ventrallv, tapering towards head ; 
except in most anterior region, dorsal contour flattened and ventral 
convex ; branchiae simple, filiform, upraised, and slightly incurved 
over the back. 
Prostomium (Fig. 77) small, conical, considerably broader than 
long, and its surface monopolized by its large appendages ; three 
pairs of antennae ; most anterior pair short, ovoid ; second pair with 
annulate basal joints and acute terminal joints about one half the 
