REPORT ON THE MY ZOSTOMID A. 
37 
as tubes 'with a crown of tubercles. All the elevations are marked out from the 
peripheral part of the ventral surface, which is blackish-brown, by their light yellow- 
brown colour. The peripheral portion is also bent upwards and radially furrowed in 
correspondence with the intestinal caeca. Through the mouth, at the anterior margin 
of the central elevation, projects the pharynx, which is provided with a subterminal crown 
of papillae of *18 mm. in length. The obtusely conical cloacal papilla at the hinder end 
of the ventral mass is further removed than the mouth from the margin of the body. The 
parapodia and suckers project equally at the commencement of the distal half of the radius. 
Host. — Actinometrci intricatci, Liitken, sp., from Tonga, 'Copenhagen Museum. 
14. Myzo stoma pallidum, Graff. 
Myzostoma pallidum, Graff, Genus Myzostoma, p. 18, pi. ii. figs. 6, 6 a. 
Hosts. — Actinometra Solaris, Lam., sp., and Actinometra parvicirra, Mull., sp., from 
Bohol (Philippines). 
15. Myzostoma marginatum, n. sp. (PI. II. figs. 16-19). 
The body is nearly circular in form and 2 mm. in extent ; both dorsal and ventral 
surfaces are alike of a yellowish-brown colour. The former is somewhat vaulted, and 
appears irregular on account of several deep furrows and a number of tubercles arranged 
close together and of various sizes ; these are only absent from a narrow transparent piece 
round the margin (fig. 16) ; the margin is provided with cirri - 18 mm. long. I was not 
quite certain about the number, but it seemed probable that they were limited to twenty. 
On the ventral side the margin of the body with its cirri is yet more conspicuous ; the 
ventral muscular mass is of a considerable size (cf. ideal cross section, fig. 19). 
The parapodia (fig. 18, p.) are of moderate size, and divided into an extremely fine 
terminal segment and a thicker basal part. Close to the third pair of parapodia are the 
conspicuous male genital papillae ( $ ). The parapodia occupy a circle nearly mid- way 
between the centre and margin of the body ; the circular suckers (s.) lie on the same level 
with the free ends of the parapodia. The oral and cloacal apertures are on the margin of 
the ventral muscular mass ; the latter is a simple opening without papillae. The small 
elevation behind the mouth shows that the pharynx is insignificant in size. 
A small yellowish-brown individual, dredged at Martinique (Station 203) by the 
“Blake,” is probably of the same species. This specimen is 1'2 mm. long, and has all 
the characters of the species, but less sharply marked. There are ten pairs of cirri, arranged 
m regular order, the largest of which measured ’1 mm. The terminal segments of the 
parapodia are sharply marked off from the basal as little button-like portions. 
Host. — Actinometra discoidea, P. H. C., from Station 155 (Montserrat) of “Blake” 
Expedition. In this case the parasite was attached to the host. I have also a specimen 
