30 
THE VOYAGE OE H.M.S. CHALLENGER. 
and ventral surface, which sometimes inclines to green. The back is divided by a series 
of furrows into polygonal areas, which are continued for a short way on to the ventral 
surface. 
Host . — Uncertain. Dredged in the Chinese Sea. 
4. Myzostoma labiatum, n. sp. (PL II. fig. 23). 
This species is not unlike Myzostoma lutkeni, but differs from it in that the ventral 
elevation does not differ in colour and consistency from the rest of the ventral surface, 
and that the parapodia (p.) and suckers (s.) are further out. 
The suckers also are smaller than in Myzostoma lutkeni , and have a finely papillose 
margin. 
The uniformly greyish-brown body is somewhat more than 4 mm. in diameter ; it is 
circular and unprovided with cirri. On the dorsal surface is a median elevation, and on 
each side five elevations corresponding to the parapodia. On the ridges formed by 
these latter the folds, which are developed over the whole body both above and below, 
take the shape of small wart-like processes. The pharynx (ph.) is distinctly visible, with 
the crown of papillae, and makes the resemblance to Myzostoma lutkeni still more obvious. 
A closer examination shows that these papillae (fifteen to be seen from the ventral side, 
the longest measuring ‘3 mm.) belong really not to the pharynx but to the margin of the 
mouth, and therefore at once serve to distinguish this species. The conical cloacal papilla 
is very prominent, and lies at the same distance from the margin as the suckers. 
Host . — Probably Antedon incequalis, P. H. C. Dredged by the Challenger Expedi- 
tion at Station 174, south-west of the Fiji Islands. 
5. Myzostoma echinus, n. sp. (PL II. figs. 29-30). 
This is one of the most remarkable species, owing to its size and the sculpturing of 
the back. The body is nearly hemispherical, with a flat ventral side of 5 mm. diameter. 
The back is grey inclining to brown, and very finely folded to form irregular lines, which 
are conspicuous and visible even with a simple lens. The dorsal surface is also orna- 
mented by high cylindrical tubercles of a brown colour and considerable hardness. These 
tubercles bear smaller tubercles upon them, which are sometimes ramified. The arrange- 
ment of these tubercles corresponds to the structural arrangement of the body. First there 
is a median rank, running from the anterior to the posterior end of the body ; on either side 
of this are five longer rows, each containing seven to ten tubercles and corresponding to 
the parapodia ; between them are shorter lines containing three to five smaller tubercles, 
which correspond to the suckers. Occasionally several tubercles of one row are joined by 
continuous ridges of the colour and consistence of the tubercles themselves. The flat 
ventral surface is folded (fig. 30) like the back, but the smaller folds are not so distinctly 
