208 
THE VOYAGE OF FI.M.S. CHALLENGEE. 
The head (PI. XXIX. fig. 6) is somewhat small, the frontal margin unbroken, though 
slightly notched interiorly, and there are two very distinct brownish eyes on each side 
arranged in the limbs of a Y. The anterior pahyare considerably larger. Just in front 
and to the inner side of each of the latter is an antenna, the base of which is. thus con- 
siderably behind the frontal margin. They are moderately thick, curved outward, and 
show no traces of annulation. The tentacle is absent. The buccal segment bears a pair 
of cirri on each side, the inferior being shorter. The ch’ri have been removed from tbe 
next segment, but their bases are very large and distinct. The mouth opens as a longi- 
tudinal slit behind the axial groove on the snout. 
The first I’oot follows the buccal cirri, and as usual it and several of its successors are 
furnished with longer cirri. Y^hen fuUy developed^ each foot (PI. XXXIII. fig. 5) forms 
a thick process, with a short dorsal cirrus, but without a differentiated ventral one. As 
formerly indicated, the region of the ventral cirrus on each side is occupied by a thick 
pad which extends over a third of the transverse diameter, the central and somewhat 
wider region being depressed, the whole forming an arrangement similar to that in the 
Sabellidae and Terebellidae. The dorsal cirrus is slightly tapered, and • has no trace of 
annulation. The basal region (pertaining to the body-wall) is short. The rest of the 
foot forms a thick mass with a dimjole opposite the tip of the spine, the upper region 
being convex, and the lower sloping inward to the body. The spines are pale and 
slender. The fifteen short bristles pass outward beneath the notch, and have the distal 
ends of the shafts dilated and furnished with a short bifid appendage (PI. XYa. fig. 15). 
The feet on the whole seem to undergo little modification from the front to the ternuna- 
tion of the body. The tail has two short cirri on each side of the anus, which is 
terminal. 
In transverse section the body is found to be distended with the reproductive 
elements (apparently male). The nerve-area is comparatively superficial, and thus in 
contrast with the common British species, a form allied to Syllis armillaris, 0. F. Miiller, 
in which the ventral muscles almost meet in the middle line outside the cords. The 
distention from the growth of the reproductive elements, however, may to some extent 
alter the relation of the parts. 
The bristles resemble those of Autolytus, and the form of the feet and other parts 
seem to point its connection with that genus. 
Family Nereid a:. 
The representatives of this large family are comparatively few, indeed only about half 
the number described by Prof. Grube in his Annulata Semperiana from the Philippines. 
This disproportion is probably due to the fact that the Nereides abound in shallow water 
