302 
THE VOYAGE OF H.M.S. CHALLENGEK. 
border. Both accessory plates are toothed. The left lateral impaired jhate bears 
evidences of having eight or nine minute teeth, but the edge appears to have been 
injured so that only the basal grooves are distinct. The right lateral plate has 
about ten or eleven small teeth. The mandibles (Fig. 59) have a proportionally large 
dental region, the external edge of which is produced upward, and the anterior edge 
denticulated. 
The dorsal cirri are well developed, and the same may be said of the ventral, 
upwards of twenty of the latter anteriorly have large ventral pads at the base. 
The structure of the foot (PI. XXXIX. figs. 5, 6) agrees with that in Eunice. The 
bristles are conspicuous by their dark colour. 
Anteriorly each foot has two strong brownish- 
black spines with slightly curved or hooked 
tips. Superiorly are a tuft of simple taper- 
ing bristles, and a few brush-shaped forms 
with somewhat broad tips. 
The jointed bristles (PI. XXa. fig. 17) 
have the lower part of the shaft tinted of a 
dark brownish hue, which fades to yellovush 
towards the flattened distal end. The latter 
is serrated on each side, and bears a terminal 
piece having a boldly bifid tip guarded by 
a serrated wing. The lower process of the 
bifid extremity becomes larger in the posterior 
feet. 
Besides the two brown spines in the 
posterior feet is a dark brown inferior hook (PI. XXa. fig, 18), with a powerful fang 
and a short process above it. The two latter are guarded by a wing on each side. 
In this form the cuticle is dense and the hypoderm very feebly developed except 
on the appendages. The nerve-area is large and rounded, with apparently a considerable 
neural canal like a slit toward the lower part of the circle. The oblique muscles meet 
above the cords, while a muscular fasciculus passes downward on each side. The general 
structure is typical. 
This species seems to differ from any of those described by Kinberg, all of which 
come from the Pacific. Grube does not appear to have fully appreciated the char- 
acters of Nicidon, for he places the representatives doubtfully after the Eunicidse 
with articulated tentacles, which have few (not more than four) branchial filaments. 
The Eunice madeirensis of Baird (British Museum, no locality) agrees in the absence 
of branchiae, but it seems to have articulated dorsal cirri, i.e., they have a median 
constriction in the preparation. In another closely allied example from Madeira in the 
Fig. 58.— Maxillng and dental plates of Nicidon balfouriana< 
n. sp. The right lateral plate has been deprived of its bound- 
ary-line ; X 20 diameters. 
Fig. 59. — Mandibles of the same species ; x 20 diameters. 
