324 
THE VOYAGE OF H.M.S. CHALLENGER. 
The appearance of the post-cephalic region of the dorsum resembles that of an 
Eunice, from the great development of the branchiae, but the ventral surface, 
especially anteriorly, is at once diagnostic. The first four feet embrace a region of 
their own, apparently corresponding to that formed by the first two in a new British 
form, ancl in many of the preceding species. These feet are much less prominent than 
the ordinary examples, and, indeed, each foot is ventral rather than lateral. The region 
is easily differentiated from the succeeding one by the presence of the ventral scutes. 
Instead, moreover, of the strong projecting bristles so characteristic of the common 
forms, each setigerous process, from the first to the fourth, bears a tuft of incon- 
spicuous bristles which are directed downward (ventrally) rather than outward. The 
ventral cirri and setigerous processes of these (four) feet diminish in size from before 
backward, but the dorsal cirri do not alter much. The latter are thickish, knife- 
shaped processes of moderate length, and considerably stouter than in the ordinary 
form. The setigerous lobe bears posteriorly an elongated conical process, which also 
diminishes from before backward. The ventral cirrus is somewhat conical, and, as in 
Nothria conchylega, ceases with the region, indicating that the first scute, which 
occujjies the same position, is homologous therewith. Each setigerous process bears 
two or three stout spines, on the convex margin of the tuft, followed by a series of 
rather short bifid bristles (PI. XXVIa. fig. 1) with an evident curve. The forked tip is 
composed of short rounded processes, the distal being the longer. The entire extremity 
is guarded by a sheath or “ wing,” which is best seen from the dorsum (PI. XXVIa. 
fig. 2). An articulation occurs some distance below the tip, as in Nothria tenuisetis. 
These four sets of bristles point ventrally in the specimen (which has been preserved in 
situ, that is to say, within its habitation), and are probably of service to it in its various 
movements near the mouth of its tube. 
The succeeding region of the body commences at the fifth foot, and is characterised 
by the elongation of the dorsal cirrus, and the conversion of the ventral into a flattened 
glandular scute. The first scute is less than the others, but they rapidly increase in 
size, so that between the fourth and the tenth they attain their maximum, and again 
somewhat diminish posteriorly. They are most conspicuous in front of the fortieth foot, 
though they continue to the end of the fragment (beyond the seventieth foot). 
At the tenth foot (PI. XLI. fig. 8) the dorsal cirrus forms a long subulate process 
with a constriction at the base, which is supported internally by a tuft of simple bristles. 
Just above the enlargement at the base is a deposit of pigment, which becomes more 
distinct in the succeeding feet. The setigerous process has two groups of bristles, an 
upper longer and an inferior shorter series. Both conform to the same type, viz., bristles 
with stout shafts and tapering extremities, and furnished with boldly striated wings, the 
tips of the inferior, however, being much shorter than the superior. The branchial process 
appears at the seventeenth foot, springing from the constricted part at the base of the 
