POLYCELETA—BENHAM. 
99 
These structures appear to be the “ areolae ” of Grube’s account of PJiyllocomus 
crocea (1877, p. 543), and the relative disposition of them seems to correspond to 
the three structures figured by McIntosh (1885), pi. XLYII, fig. 11), which he 
interprets as the bases of lost “ gills.” 
These three pairs of channels and tunnels appear to be unique, and I regret that, 
having only a single specimen of the worm, I am unable to examine them by sections. 
I have no suggestion to make as to their purpose. The worm is well preserved, and 
there is no evidence of rupture here, no suggestion that any structure, such as a gill, 
has been broken away; the margins of the channels are rounded and smooth, and appear 
quite natural. At any rate, under the highest power of a dissecting microscope I can 
see no sign of any interruption in the continuity of the surface. 
The tentacles, as is usually the case in the family, are invaginated into the 
buccal cavity. They were exposed by slitting up the side of the body along a line 
corresponding to the junction of the lower lip with the peristomium (fig. 113). TLen 
numerous filamentous tentacles are seen directed backwards along the roof of a cavity, 
which I suppose is the buccal cavity; they are borne by a rounded ridge, which extends 
across the base of the prostomium, curving forwards on each side till nearly in the line 
of the lateral margin of the lower lip (fig. 116). 
Within the lower lip, along its base, is a second rounded ridge which connects 
right and left with the tentacular ridge; it is apparently a sphincter muscle, and may 
be exaggerated by the contracted Aate of the worm. 
The tentacles are 10 mm. in length and are united to one another for a distance 
of about 3 mm. from their origin, where they are only indicated by lines separated by 
shallow furrows. The proximal portion of the tentacles is surrounded by a thin 
membranous flap, 1 mm. in height, springing from the tentacular ridge; and when 
the tentacles are lifted up a line of brown-red pigment-dots is seen close to its free 
margin on its tentacular surface; further, a second line of darker spots lies along its 
base, close to the roots of the tentacles (fig. 117). 
The body.-—The dorsal surface is smooth, annulate and without inter-segmental 
furrows, but the segments are distinct enough laterally and ventrally ; the body is 
very strongly arched, so that the notopods are directed upwards ; the third segment, 
like the next two, is much narrower than the following, though whether this is again 
due to the strong contraction of the worm seems doubtful, in light of the statement by 
Grube that in his species these three segments are shorter than the rest. 
The third segment carries the first notopod, which is smaller than the following, 
and bears only a few chsetaj. The next two notopods are likewise small, but the number 
of chgetae increases ; the maximum is attained at about the sixth or seventh, and this 
is retained until the fourteenth. 
The bristles are long, stout and of a golden-yellow colour ; they are arranged in 
a single vertical series with longer ones above and successively smaller ones below. 
