PRAXILLELLA GRACILIS. 325 



It ranges to the Gulf of St. Lawrence, Canada (coll. Dr. Whiteaves) ; Norway and 

 Finmark (Malmgren) ; Spitzbergen, East and Av^est Greenland (Arwidsson) ; Norway 

 (Sars) ; United States of America, New England (Verrill) ; North Sea (Ehlers) ; West 

 Indies (Augener) ; N. E. America (Moore). 



The head (Plate C, fig. 5) has the cephalic plate somewhat more oblique than in P. 

 prmtermissa, so that the anterior border is more acute in lateral view, especially as the 

 filament and anterior process thus appear as a continuous narrow appendix. In the median 

 line anteriorly is the flattened conical prow seen in the form above mentioned, but it has 

 distally the filiform process so characteristic of the species. From the basal process the long 

 and rather narrow glandular keel passes backward almost to the posterior border. The 

 long nuchal organs lie at each side, and they slightly bend outward anteriorly, but do not 

 reach the margin which has two broad lateral flaps in front of the notches, and a narrower 

 and often more or less erect border behind the notches. The fused pro- and peristomial 

 segments have the large aperture of the mouth ventrally, and it is usually marked by a 

 series of radiating furrows which are somewhat regularly arranged on the prominent 

 posterior lip. Anteriorly a ridge runs forward to the notch on each side of the flattened base 

 of the anterior process. In partial protrusion the proboscis forms a button-shaped papillose 

 organ, but in full extrusion a considerable bladder-like, smooth region with a terminal 

 fissure occurs beyond it. The papillae on the basal region in extrusion are bluntly conical, 

 large and prominent ; four to five papillse being in each row anteriorly, and nine or ten 

 occurring, as Arwidsson observes, in each row posteriorly. Reddish mud oozed from the 

 mouth on the slightest pressure. The fine mud swallowed by the annelid contains many 

 organic elements besides spicules of sponges and minute sand-grains. An occasional 

 larval annelid is met with in it. 



The body is more or less rounded dorsally, slightly flattened behind the anterior third 

 ventrally, and marked by a median streak, which becomes a ridge posteriorly. A distinct 

 constriction behind the cephalic region affecting three or four segments occurs anteriorly. 

 There are nineteen bristled segments, and four without bristles posteriorly. Large forms 

 exceed 100 mm. in length, and the walls of the body posteriorly are thinner than in P. 

 prater nrissa, so that from flattening the diameter in large examples is 4 to 5 mm. The 

 anal funnel (Plate CI, fig. 5 a) is comparatively small, has a prominent anal cone with a 

 valve, a long ventral cirrus, and twenty-two to twenty-five (Arwidsson gives twenty- 

 seven) shorter cirri, which vary in length in different specimens. Pigment is usually 

 absent in spirit-specimens, but in one the anterior region is mottled with brownish-red. 

 The anterior bristled segments from the first to the eighth are glandular, but the glandular 

 elevations at the rows of hooks thereafter are absent. Arwidsson gives in detail the 

 arrangement of the glands in the various parts. The segmental organs occur in bristled 

 segments 6 to 9. The first, second, and third segments are, as mentioned, firm, rounded 

 and glandular, the ventral streak forming a ridge rather than a groove. Each has a 

 short row of hooks and a tuft of rather long bristles (Plate CIX, fig. 12), which are in two 

 groups, a stronger golden series with nearly cylindrical shafts, except the somewhat 

 narrowed region at the base, and tapering and slightly curved tips with narrow wings, and 

 a more delicate series having slender tips with a trace of wings. The hooks of the three 

 segments differ from the succeeding in the absence of the gular bristles, in the great size 



