510 
THE VOYAGE OF H.M.S. CHALLENGER. 
The body is wide in the thoracic, somewhat fusiform in the abdominal region, that is, 
slightly narrowed at the commencement, dilating as we proceed backward, and again 
diminishing more decidedly toward the tail. 
The thoracic region consists of seven segments, draped on each side by the great 
membranous lamella, which projects far beyond the bristles, and ventrally forms a broad 
apron across the anterior part of the abdominal division. The dorsal surface of the 
region is smooth. The ventral presents somewhat festooned borders from the interruption 
of the folded membranous lamella opposite each foot. Just in front of the plait or apron 
which overlaps the anterior border of the abdominal region is a tessellated area of limited 
extent (in those best developed about half the breadth of a segment). 
The bristles are pale yellowish, the dorsal having extremely attenuate tips, with just 
a trace of wings, the inferior having peculiarly flattened and rather short extremities 
(PL XXXIa. fig. 12), the winged region being less differentiated than usual in such forms. 
A double line below the broad falciform tip, and a slight indication of wings near the 
ventral edge of the latter, however, are present. The shaft of the bristle narrows 
below the tip, and slightly enlarges toward the insertion interiorly. They are slender. 
The posterior bristles, again, are likewise elongated structures with tapering tips, which 
have no distinct traces of wings. Each bristle-tuft springs from a prominent foot-papilla, 
which is flattened antero-posteriorly, and presents a dorsal and a ventral ridge. 
The abdominal region is dorsally also somewhat rounded or convex transversely, and 
deeply furrowed by a broad flat groove along the ventral median line. 
The anterior uncinigerous pads commence at the third bristle-tuft (a small papilla 
which occurs below the second tuft being devoid of hooks). The latter (PL XXXIa. 
fig. 13) differ from those of the British form in the greater elevation of the crown, and in 
the short and well-marked process behind the great fang. The curvature of the body 
behind the latter is also quite different from that in the British species, and whereas the 
■sinus below the great fang is long in the latter, it is short in the present form. 
The fine greenish-grey mud in the intestinal pellets showed sponge-spicules. Diatoms, 
and minute ova. 
No tube is present. 
The structure of the body-wall in the anterior third somewhat diverges from that in 
the British Protula jproteyisa, in which the dorsal muscles are very massive. The nerve- 
cords, however, occupy a similar position, viz., at the inner edge of the longitudinal 
ventral muscles. The wide interneural area is occupied by the basement-tissue of the 
region, fibres from the sheath of the alimentary tube, and a thin stratum of longitudinal 
fibres. Externally are a thin layer of circular fibres and the hypoderm. The ventral 
blood-vessel lies within' the circular coat. Posteriorly the longitudinal dorsal muscles 
approach each other more closely in the middle line, and each forms a more extended 
lamina. The nerves are as widely separated as in front. The great development of the 
