REPORT ON THE MY ZOSTOMID A. 
45 
body is perfectly circular, thin, brownish-yellow coloured with a broad transparent mar- 
ginal zone. The largest of the three specimens is 1 mm. in diameter, the smallest *6 mm. 
There are twenty thick obtusely pointed cirri of equal length (in the larger specimen 
•9 mm., in the smaller '05 6). Their bases are continued for some way into the interior of the 
disk. In the intervals between the cirri, the margin of the body is prolonged into rounded 
lobes. The parapodia ( p .) are comparatively well-developed, and are arranged in a circle 
at about the inner third of the radius; outside are the large .oval suckers ( 5 .), distant 
from the margin about their own length. The mouth (m.) and cloaca! aperture (cl.) lie 
at the same level as the suckers. The pharynx ( ph .) is well-developed ; the male genital 
papillm ( ) form two tubes of the same length as the parapodia, and reaching to the 
margin of the body. 
Host. — This species was found in bottles containing Crinoids collected at Station 203 
(Martinique) of the “ Blake ” Expedition, and in bottles containing Crinoids dredged by 
the American telegraph steamer “ Investigator,” under the command of Captain Cole, near 
St. Lucia, in lat. 13° 22' N., long. 61° 7' W. ; 278 fathoms. (Both belong to the Museum 
of Comparative Zoology, Cambridge, Mass.) From P. H. Carpenter’s list of the Crinoids 
dredged at these two Stations it appears that Actinometra meridionalis, A. Ag., is the only 
species that occurs at both Stations, hence it is probably the host of Myzostoma crenatum. 
30. Myzostoma ivyville-thomsoni, n. sp. (PI. VI. figs. 1, 2). 
Both the specimens that I had in my possession were much damaged, and fig. 1 is 
therefore “ restored.” This species is thin and fragile, and of a dirty- white colour. In 
the middle it has the thickness of a small Myzostoma cirriferum ; the portion lying out- 
side the suckers, which are placed very far inwards, is delicate and transparent ; there 
is, however, no precise line of division between the two. There are twenty strongly 
developed cirri, the first and second pairs of which are situated at a greater distance from 
each other than the rest, and are remarkable for their large size (as much as ‘6 mm. long); 
the base is continued into the ventral surface. The body is oval, and 2 '3 mm. long by 
1'7 mm. broad. The parapodia (p.) are somewhat remarkable ; they are '7 mm. in length, 
and the large basal part, which includes the manubrium and its muscles, is sharply marked 
off from the narrow terminal portion, which is often bent or rolled. It is very clear that 
the slender hook emerges from the distal end of the basal portion and not from the 
terminal portion, since the latter is furrowed and not tube-like ; the hook lies in this 
furrow, but emerges from it when it commences to be twisted. The largest hooks 
measure *015 mm. thick and ‘56 mm. long; they are clear and transparent. The tip is 
rather bent and somewhat swollen at the anterior end before the bending (fig. 2) ; this 
is the thickest portion of the whole hook. The mouth (m.) lies a little outside the circle 
of the suckers ; the pharynx (ph.) is nearly one-third of the entire length of the body. 
The branches of the intestine and the genital apparatus I did not see. 
