REPORT ON THE ANNELIDA. 
391 
It differs conspicuously from any of tlie previous forms in having branchiae arranged 
in the form of a tuft on each side, on the ventral aspect. The segments are narrow, 
consisting of a smooth dorsal arch cut by two transverse furrows into three divisions. 
Just as the arch bends down laterally a prominent ridge (bearing hooks) occurs, and 
after an interval another elevated soft ridge lies above the branchiae. At the summit 
(dorsal and very prominent) is an isolated papilla. A dense branchial tuft is situated 
at the lower border of the foregoing ridge in each segment. These are short, slightly 
branched processes, with much corrugated external walls, the transverse wrinkles being 
probably due to the contraction of the longitudinal muscular fibres, which are very 
distinct in many of the preparations. No evident blood-vessels are noticed, but most 
are filled with an opaque central mass composed of brownish globules and granules, 
probably blood. The perivisceral fluid contains larger corpuscles. The ventral arch is 
completed by a narrow ridge between the branchiae of 023posite sides, the hook-bearing 
portion being more prominent than the rest. 
The dorsal and ventral hooks agree in structure (PI. XXIVa. fig. 17), but both are so 
minute that their exact nature is not readily determined. The crown seems to have 
only one s^une above the large fang. The form of the shoulder and shaft approaches 
that of a Notomastus from the coast of New York. 
The greyish mud with which the intestine is filled presented sand-grains. Diatoms in 
great profusion, fragments of sponge-spicules, Eadiolarians, and other structures. 
The cuticle and hypoderm are somewhat thin in proportion to the size of the body, 
but the circular muscular coat is well marked. A considerable ventral longitudinal 
muscle occurs on each side, the thickest mass being situated close to the median fissure, 
at the wide inner part of which the nerve-cords lie. The dorsal longitudinal are thinner, 
and, like the ventral, are somewhat coarsely fasciculated. 
The imperfect condition of the specimen does not permit a decisive opinion with 
regard to its relationship with other species. It appears to be closely related to the 
ordinary species, viz., Dasyhranchus caducus, Grube, and also to the forms described by 
the same author from the Philippines.^ 
Family Maldanida:. 
The members of this family have occurred in the collections of most exploring 
expeditions, though seldom in great numbers, probably because they are not amongst 
those readily observed in the contents of a dredge. Compared with other expeditions, the 
representatives of the group in the Challenger are remarkable for their number, as well 
as the great depths to which not a few descend. Indeed some of the forms, such as 
Nicomache henthaliana, are amongst the dwellers in the great deeps, e.g., 2300 fathoms, 
1 Op, cit., p. 189, &c. 
