REPORT ON THE ANNELIDA. 
513 
The branchiae are united by a web at the base, and form two masses of slightly 
twisted radioles, which have a smooth tapering filament at the tip. The dorsal edge of 
the cephalic collar forms a large and somewhat fan-shaped flap, and is separated by a deep 
notch at the lateral region from the ventral division. The latter is less prominent in the 
middle than at the sides, but the edge is entire with the exception of a few frills. It 
seems to present the usual relations in the thoracic region. 
The bristles of the anterior division (PL XXXI a. fig. 19) are of a pale yellow colour, 
and have very delicately tapered tips, only distinguished from the shaft by a slight 
curvature. The wings are very narrow. The developing forms have broader tijDS. The 
posterior bristles show the usual linear form, and their tapered extremities are slightly 
curved. 
The anterior hooks (PI. XXXIa. fig. 20) present an elevated crown, which is slightly 
bulbous toward the summit, a deep dorsal concavity and numerous small teeth above the 
great fang. The latter does not project so far beyond the prow as in Protula capensis 
or Protula lusitanica. The general outline of the hook is less rhomboidal than in the 
former species. The crown is more elevated, and the great fang less produced at the tip 
than in the Protula from St. Andrews. 
The posterior hooks diverge very little from the foregoing. The dull greyish sandy 
mud in the alimentary canal contained numerous Diatoms and a few Kadiolarians. 
The species inhabits a comparatively smooth, coiled tube, marked here and there by 
wrinkles and soldered to other tubes or its own coils. This is unusual in the Protula 
of British waters, though it is not a feature of much moment. 
In transverse section the body-wall at the termination of the anterior third presents 
a considerable thickness of hypoderm, especially ventrally, the deeper region character- 
istic of the latter commencing, externally, on each side about the middle of the ventral 
longitudinal muscle. The circular muscular coat is thin but distinct. The longitudinal 
dorsal are proportionally less bulky than in such as Protula arafurensis, and they are as 
massive superiorly as inferiorly. More than a third of each muscle leaves the circular 
coat inferiorly and rests on the oblique, so that a part (thin edge) overhangs the outer end 
of the longitudinal ventral. The inner edge superiorly is pointed, and separated by a 
wide hiatus from its fellow. The longitudinal ventral muscles are not quite half the bulk 
of the former, and are elongate-ovoid in shape. The nerve-cord lies against the inner 
border, and intervenes between them and the neural canal, though a thin stratum of 
longitudinal fibres, as in certain other species, passes externally to both nerve and canal, 
and appears almost to join that of the opposite side. The neural canal contains the usual 
coagulable fluid. Within the circular muscular coat dorsally is a firm though thin band 
of fibres which courses on each side along; the inner margin of the longitudinal dorsal 
muscle, joins the oblique fibres from the outer surface of the latter at its inferior border, 
and slants to the ventral edge on each side of the middle line, the fibres running into 
(ZOOL. CHALL. EXP. PART XXXIV. 1885.) LI 65 
