44 
THE VOYAGE OF H.M.S. CHALLENGES. 
the largest, and from it are seen to radiate outwards a number of yellow coloured marks 
which correspond to the intestinal cseca. The intervals between the longitudinal bands 
are brownish coloured, and the intervals between the lateral ramifications are greyish-brown, 
becoming darker towards the ends of the lateral branches. The margin of the dorsal disk 
is bordered by a yellowish band. The transverse diameter of the body is T8 mm. 
Host . — Probably Antedon spinifera, P. H. C. From Station 157 (Montserrat) of the 
“Blake” Expedition. 
27. Myzostoma nigrescens, n. sp. (PI. III. figs. 13-15). 
In size, number, and arrangement of cirri, and in general appearance, this species 
much resembles Myzostoma cirriferum, differing only by its smaller length (2 ‘5) and by 
not having a translucent marginal border. The body of the single individual that I was 
able to examine is coloured blackish-brown above, and below a little lighter coloured ; 
it is thick not only in the middle of the body, but also at the margin; it is therefore hardly 
at all translucent. The parts of the hook-apparatus (fig. 14) are also much more strongly 
developed; the hook (u.) is provided with a straight extremity set at right angles to the 
rest of the shaft; it is T7 mm. long and ‘016 mm. thick. The manubrium (ma.) is short, 
measuring only T2 mm. long ; the terminal plate is distinguished by its smooth surface 
and bent edge. 
Of the twenty cirri the anterior pair are the largest, and measure 45 mm. ; the rest 
are much shorter (*27-'35 mm.). The third cirrus on the left side shows an abnormality 
already noticed by me in Myzostoma cirriferum (Genus Myzostoma, p. 79) ; it is forked 
at the extremity, one of the ends being short and stump-like, the other long. 
Host. — Actinometra morsei, P. H. C. Found by E. S. Morse in Yeddo Bay (Japan); 
the property of the Museum of Comparative Zoology, Cambridge, Mass. 
28. Myzostoma cirriferum, F. S. Leuckart. 
Hosts. — (a) Antedon rosacea. — Mr. P. H. Carpenter has specimens from Shetland 
(Bressay Sound, 5 to 7 fathoms), and Arran (5 to 10 fathoms), which 
confirm the assertion that this parasite occurs in all European seas 
where its host occurs (see Genus Myzostoma, p. 79). 
(lj) Antedon petasus, P. H. C. — -Mr. Carpenter 'has specimens from Norway, 
the Kiel Museum from Arendal, Norway; and H.M.S. “Triton” 
dredged some at Station 3 (August 8, 1882, 81 fathoms). 
(c) Antedon hystrix, P. H. C., from North Atlantic (probably cold area), 
“Porcupine,” 1869. 
29. Myzostoma crenatum, n. sp. (PI. VII. fig. 4). 
This species is one of the most elegant and regular among the flat Myzostomida. The 
