162 
THE VOYAGE OF H.M.S. CHALLENGEE. 
The specimen is fragmentary, but is larger than Grube’s, measuring 30 mm. in length 
and about 3 mm. in diameter. 
The head (PL XXVI. fig. 8) is shield- shaped, with a rounded posterior border, at 
which are a pair of small black eyes. The tentacles and subtentacles are short and 
conical. The proboscis is partly extruded in the preparation, and just in front of the 
head are a pair of muscular loops which are fixed to its base, and probably have burst 
through. The proboscis has numerous rather long papillae. The foot (PL XXVII. fig. 5) 
has superiorly a somewhat elevated lamella with a bluntly rounded free margin. The 
upper lobe is triangular, with a short tapering cirrus at the commencement of the branchia. 
The latter has an enlargement a little beyond its base exteriorly, and it is coiled inwards. 
The inferior lobe projects somewhat farther than the superior, and from its upper edge 
a branchial process, considerably less than the dorsal one, is directed upward. Like the 
other, its margins are crenate and ciliated. The lobe proper is somewhat trifid, for an 
ovate process occurs at the base of the branchia, the centre is occupied by the spine, and 
a small ovoid lamella projects between the latter and the ventral cirrus. The latter is 
dilated above the base, tapered towards the tip. There is little diagnostic in regard 
either to the shorter barred bristles or the longer serrated forms. At the bases of the 
latter are certain peculiar bifid types, which appear to be due to fractured bristles with 
tips in process of regeneration. The nerve-area in this form is wedged between the 
ventral longitudinal muscles at the sides, the oblique and vertical above, and the 
hypoderm inferiorly. It is more closely environed than in Nephthys cceca or the 
previous form. 
A similar species [Nephthys jeffreysii, n. sp.) comes from Japan, lat 33° 56' N., long. 
130° 27' E., where it was dredged by Captain St. John. The structure of the foot, 
however, shows a characteristic divergence. Instead of being rounded, the superior 
lamella has a nearly straight upper edge, the tijD is pointed, and the external border 
convex. The superior lobe of the foot is less produced than in the foregoing, the cirrus 
at the base of the branchia is symmetrically dilated at the base, and thereafter forms a 
nearly cylindrical process. The branchial organ is both shorter and more slender, and 
the enlargement a little beyond the base externally very prominent. The inferior lobe is 
very short, presenting superiorly a short, straight, branchial process which extends a little 
beyond the tip of the lamella beneath, which is somewhat conical. The ventral cirrus is 
broadly fusiform at the base, and slender distally. 
De Quatrefages, from the somewhat ambiguous figure of 0. F. Muller, ^ supposed that 
he had to do with a new type with two branchiae, and constituted the genus 
Dlplohranchus. The structure of Nephthys ciliata, however, quite differs from the 
foregoing. 
^ Zoologia Eanica, Tab. 89, figs. 1-4. 
