266 
THE VOYAGE OF H.M.S. CHALLENGER. 
segment is rather more than the breadth of the next three, has a T\"ell-defined 
sinus inferiorly, and a notch laterally at the projecting lip. In one instance, just 
below the latter, an isolated process, like a rudimentary palpus, appeared. This is an 
abnormality. 
The maxillse (PI. XXXVII. fig. 13) present a well-defined outward curve, and there 
is no abrupt bend at the tip. The left great dental plate has six, and the right seven teeth. 
The left lateral paired plate (that continuous with the two terminal or accessory plates) 
has four teeth, the unpaired has seven. The right lateral plate has nine teeth. The 
mandible (PI. XXXVII. fig. 14) is composed of two elongated, fiattened pieces, some- 
what clavate in outline, the tips being produced externally, and j^i’O’^dded with an 
irregular cutting edge. 
The first five segments behind the buccal bear simple feet. Dorsally each has a 
cirrus, articulated in a similar manner to the tentacle, and of moderate length, a median 
setigerous region, and a well-marked ventral cirrus, which is largest and longest (so far 
as these five are concerned) in the first. The sixth foot bears a minute, simple, 
branchial process near the base of its dorsal cirrus, in one example, and none on the 
seventh or eighth. In others a branchia with several branches appears on the seventh 
foot ; while in a few the tuft appears on the eighth. There is, therefore, considerable 
variety in regard to the commencement of these processes. Wherever it commences the 
tuft soon gains a number of divisions (five or six), which are proportionally of con- 
siderable length, though the whole organ is by no means conspicuous. As an illustration, 
in one example the branchia of the tenth foot had eight divisions ; that on the twentieth 
(PI. XXXVII. fig. 15) nine, one being bifid ; on the thirtieth foot nine ; on the fortieth 
seven ; on the fiftieth five ; on the fifty-sixth six ; on the seventieth six ; on the 
ninetieth twelve, and an additional (second) branchia at the base with five processes. 
The branchiae posteriorly acquire a decided increase in size, and instead of the pectinate 
form which characterises them anteriorly, their shape rather approaches that of an arbuscle. 
So far as the specimens show the branchiae are continued to the tail, only a few of the 
rudimentary posterior segments being devoid of them. 
The dorsal cirri are of average length, and present the same articulations as the 
cephalic processes, the only noteworthy change being their comparative slenderness and 
length posteriorly. The ventral cirrus soon forms a disk-like elevation or pad anteriorly, 
with a short terminal process, and such continues throughout the greater part of the 
body. Toward the tail, however, the disk-like structure disappears, and the organs 
assume the form of thickish cirri. The disk -like projection is probably of service to the 
animal (as a suctorial arrangement) in its tube, to which several members of the group 
cling tenaciously. 
The anterior feet have three black spines, often slightly curved at the tip. Each 
foot further has a series of somewhat short simple bristles (PI. XIXa. fig. 6) with a 
