5*2 
THE VOYAGE OF H.M.S. CHALLENGER. 
(A) Station 249 (Grenada) of the “Blake” Expedition, probably from Actino - 
metro, meridionalis, var. carinata, P. H. C. 
(C) Station 203 (Martinique) of the “Blake” Expedition, probably from Actino- 
metra meridionalis , var. carinata, P. H. C. 
(B) “ Blake ” Expedition, Caribbean Sea, 1 877-78 or 1 878-7 9 (label lost). Nothing 
can be stated with certainty respecting the host of this form, though it is 
probably Actinometra meridionalis, A. Ag., sp., which occurs at this Station. 
The fact that the hosts of all these forms of Myzostoma, which I have united 
under the same specific name, are so very closely allied, seems to confirm the justice of 
my view. 
41. Myzostoma, caribbeanum, n. sp. (PI. X. fig. 4). 
The single specimen that I possess has an oval thin body, equally rounded at the 
fore and hind ends; its colour is a dirty yellowish-brown, the length is 1*2 mm. and the 
breadth 1 mm. It is somewhat thicker and less transparent in the middle than towards 
the edge. There are forty-three obtuse cirri, measuring up to ‘09 mm. in length ; they 
cannot be divided into principal and secondary cirri, inasmuch as there are all possible 
intermediate conditions, from minute tubercles up to the longest cirri. At the hinder 
extremity is an unpaired median cirrus ( C '.). The parapodia (p.) are feeble, and occupy 
nearly the middle third of the radius. The round suckers ( s .), which are small but very 
distinct, are in the middle line between the bases of the parapodia and the margin of the 
body. On the same level with these are the mouth opening (m.), the cloaca (cl.), and 
the obtusely ending genital papillae ( $ ). 
Host. — Uncertain. “Blake” Expedition, Caribbean Sea, 1877-78 or 1878-79 (label 
lost). 
42. Myzostoma rotundum, n. sp. (PI. X. fig. 2). 
The animal is nearly circular, and of a yellowish colour at the margin, inclining to 
brown in the middle of the body ; its length is - 832 mm., diameter '88 mm., it is therefore 
one of the smallest species of the genus. The marginal border is prolonged into a 
number of short obtuse cirri, the longest of which measure '08 mm., while the smallest 
are minute tubercles. The single specimen has altogether fifty-one cirri, arranged in 
quite an irregular fashion ; the large and small cirri are at unequal distances and bear 
no relation to each other in their arrangement. The pharynx (ph.) is large and con- 
spicuous, as also the stomach, cloaca (cl.), and the ten intestinal caeca (?'.), especially on one 
side. The parapodia (p.) are relatively feeble, and occupy a circle at the inner end of the 
middle third of the radius ; the large round suckers ( 5 .) lie at the boundary of the middle 
and the last third of the radius, as also the mouth and cloacal aperture (cl.). 
