416 
THE VOYAGE OF H.M.S. CHALLENGER. 
and extends along tlie anterior palpi. Just behind the lanceolate cirrus on each side is a 
tuft of beautifully pinnate bristles (PI. XXVa. fig. 18). The pinnae slant very regularly 
in a distal direction ; while a few transverse markings occur in the shaft inferiorly. 
Dorsally the mottled brownish cephalic bars or markings are continued evenly 
backward in the median line a considerable distance, so that there is no separation of 
the cephalic region on this surface. Laterally, however, a branchial appendage indicates 
a distinction, and on each side, below the latter, are three processes, viz., a dorsal, 
ventral, and median, the two former being more filiform than the latter. The separation 
is completed by a fold which, on each side, runs inward ventrally to the mouth. These 
lateral appendages probably indicate a segment, and the tuft of bristles on each side of 
the mouth may be the ventral bristles pertaining to it, though in such a case the lateral 
palpi at the mouth must have passed forward into the buccal segment. The fact, 
however, that these bristles differ very decidedly from the following series would show 
that there is no necessity for strictly connecting them with the first body -segment. 
The next three segments are well defined, each bearing the usual pair of branchiae, 
the dorsal tuft of strong bristles and the lateral lappet, with its ventral group of more 
slender bristles. 
The dorsal bristles (PI. XXVa. fig. 19) form a linear series of stout flattened oar- 
shaped organs, widening gradually from the base upwmrd to the tip, the latter, how^ever, 
being drawn to a short point. The edge of the thin flattened region at the extremity (a 
modification of the ordinary wings) is hispid with minute spines, which extend for some 
distance downward on the blade. Between each of these is a minute bristle 
(PI. XX Va. fig. 20) more decidedly resembling an oar, and with proportionally longer 
spines on the tip. The shaft is distinctly narrow^ed beneath the terminal region or blade. 
The ventral tuft of bristles, though smaller, conforms to the same type ; the tip , 
however, is much more tapered (PI. XXVa. fig. 21), and furnished with longer spines 
than the corresponding series in the dorsal tuft. In the same way, the more slender 
intermediate bristles assume a pennate aspect, somewhat after the manner of the ventral 
buccal tuft, but more finely spiked. A complete series of gradations is thus clearly seen 
in these bristles, from the boldly pennate ventral, to the less pennate intermediate 
ventral forms, then to the boldly hispid oar-shaped kinds, and finally to the stout dorsal 
series, where all that remains of the pennate arrangement is a slightly hispid tip, only 
detected by careful examination. 
The posterior region of the body follows the last mentioned, and in it the dorsal 
bristles are absent. A ridge for hooks extends from the base of the branchiae in front 
downward to the ventral surface, the process beyond terminating in a filiform cirrus, 
followed by a tuft of long delicate, tapering bristles with regular spinous rows. In each 
tuft there are a few more finely spinose than the rest, both forms being shown in 
PI. XXVa. fig. 22, a, b. These bristles continue to the posterior end of the animal. 
