406 
THE VOYAGE OE H.M.S. CHALLENGEE. 
The first three segments behind the buccal form the anterior region, and have simple 
stout, spines interiorly, which in the third amount to four. The spines are slightly 
oblicj[ue at the tip. These three segments are of moderate length, and the second and 
third have free anterior margins, forming in each case a collar for the preceding- 
segments. The succeeding five segments are conspicuously marked by a white band at 
the anterior margin, in front of the rows of hooks, and nearly the whole of this in each 
constitutes the collar round the base of the preceding segment. The anterior segments 
(so far as they are present) are short, jorobably from contraction in spirit. The ventral 
surface is marked by the usual pale band, which in a few of the anterior segments 
merits the name of a ridge. 
The rows of bristles present for the most part an alternation of stout and slender 
forms. The former have peculiarly modified, narrow wings, followed by a slight enlarge- 
ment, and very long and finely tapered tips. On the other hand, the latter are simple 
tapering bristles without evident wings. 
The uncini (PI. XXVa. fig. 6), in j>rofile, show about five teeth above the great fang. 
The fibres arise close under the latter. The distal region of the hook is comparatively 
long, and the shoulder well marked. 
The food of this form is peculiarly rich in various Diatoms, small and large, sponge- 
spicules, and other organic debris. Few sand-grains occur in the pulpy greyish mass. 
The contrast between the foregoing food and the same materials composing the 
exterior of the tube is striking. The coarser, larger, and rougher spicules of sjDonges 
glisten all over the latter like minute hairs, while Diatoms in great numbers, rounded 
bodies (Kadiolarians ?) like ova filled with coarse yellowish granules, and the chitinous 
walls of which are devoid of sculpturing other than the very minute dots seen in many 
ova, and a few sand particles are amongst the most conspicuous features. The tube 
is friable and mostly membranous. Its anterior region is formed chiefly of the secretion 
of the animal. 
In the general configuration of the body-wall on section, this form approaches 
Praxilla kdllikeri. The circular muscular layer, however, appears to be thicker, and 
the nerve-area is kept outside the tense line of this coat ventrally. The bulky region 
of both dorsal and ventral longitudinal muscles is inferior, each tapering in its progress 
upward, a feature prevalent in the group. The oblique muscles are inserted just outside 
the nerve-area. The perivisceral corpuscles are mulberry-like with nodular surfaces. 
Praxilla assimilis, n. sp. (PI. XL VI. fig. 9 ; PI. XXVa fig. 7). 
Hahitat . — Dredged at Station 149h, off Cumberland Bay, Kerguelen Island ; lat. 
48° 45' S., long. 69° 14' E. ; depth, 127 fathoms ; surface temperature, 39°‘8 ; sea- 
bottom, volcanic mud. 
