40 
TIIE VOYAGE OF H.M.S. CHALLENGER. 
liagen Museum. They were all of equal size, about 3'5 mm. long, and differed from the 
Bohol specimen in their yellowish-brown colour, opaqueness, and larger size. One speci- 
men had the dorsal surface finely granulated ; and a renewed examination of the speci- 
men from Bohol, formerly described by me, showed granulations here and there. 
Hosts. — (a) Actinometra parvicirra, Mull., sp., from Bohol (Philippines), (b) Uncer- 
tain. The Copenhagen specimens were taken from Crinoids (. Actinometra , Antedon) 
from the central part of the Southern Sea (Tahiti, Samoa, &c.), but no more exact state- 
ments can be made. Two other smaller individuals (2 '27 mm. long) I got from an 
undetermined species of Comatula from the British Museum. The locality, however, was 
unknown. 
20. Myzostoma coriaceum, n. sp. (PL XL figs. 1-3). 
By the permission of Dr.. A. Gunther, L received from Prof. Jeffrey Bell three speci- 
mens of a Myzostoma found by Mr. P. H. Carpenter on an Antedon (. Antedon insignis, 
Bell, MS.) dredged during the “ Alert ” Expedition ; this is the largest species known to 
me. The diameter of the circular body is about 9 mm., and as the margins are bent 
down, the animal must really measure as much as 1 cm. when fully extended. The 
colour is a darkish brown, only a marginal zone about '3 mm. wide being of a somewhat 
lighter colour, but not in the least transparent. The dorsal surface has irregular folds, 
caused no doubt by the alcohol ; the skin is smooth and without tubercles. The con- 
sistency of the body is very much that of leather, but the thickness is inconsiderable, — 
this species is in fact almost the thinnest known, as may be seen from the ideal cross 
section (fig. 3). The margin of the body has twenty cirri, measuring from ‘2S-’S mm. 
in length, and it is a curious fact that the smallest specimen, 2 ‘.7 mm. in diameter, has 
cirri proportionally far larger ; they measure about ‘22 mm. long. The parapodia (p.) 
are near the centre of the ventral surface at about the end of the inner third of the 
radius. From the external margin of their insertion to the tip they measure about "7 mm., 
and are in consequence relatively small. Slightly outside of the parapodia, about half-way 
between the margin and the centre of the body, are the prominent rounded suckers ( s .), 
- 3 mm. in diameter ; they are conspicuous by the fine folds on their free surface. At the 
same level as the suckers are the oral (m.), cloacal (cl.), and two male genital ( $ ) apertures; 
the latter are situated at the extremities of papillae considerably larger than the parapodia. 
Host. — Antedon insignis, Bell, MS., from Station 110 (Port Denison, 3 to 4 fathoms) of 
the “ Alert ” Expedition, British Museum. 
21. Myzostoma radiatum, n. sp. (PI. III. figs. 12, A, B ). 
The form of this species is very peculiar ; the back is flat, while the ventral surface is 
vaulted (see ideal cross section, fig. 12 ,B). Seen from below (A) this massive swelling is 
intersected by ten radial furrows, dividing up its area into as many sectors, each of which 
