of Edinhirgh, Session 1883-84. 
379 
3. Myzostoma alatum, sp. n. 
Hab. Antedon phalangium. The Minch. August 14, 1869. 
60 to 80 fathoms. 
Station 13, 1870. Lat. 40° 16' K, long. 9° 37' W. 220 
fathoms. Temp. 52° F. 
A species belonging to the type of Myzostoma glahrum. Dorsal 
surface arched and the ventral one hollowed, with a small muscular 
prominence in the centre. It is unprovided with cirri, and not 
transparent at the margin. Mouth ventral and cloacal papilla 
dorsal as in M. glahrum. Colour dirty yellow. Parapodia ex- 
tremely short and reduced to annular folds, from the middle of 
which there project the brownish-black points of well-developed 
booklets. These are closely grouped around the central muscular 
prominence ; while the round suckers lie near the edge of the 
ventral surface. 
A fully grown individual, 4 mm. in diameter, was so firmly 
attached to the disc of its host near the mouth that the booklets 
remained in the perisome when it was removed. On its back was a 
young one measuring 1 mm. in its longer diameter. This differs 
from the adult in the presence of distinct papillae on the dorsal 
surface, separated from one another by considerable intervals. 
4. Myostoma pulvinar, sp. n. 
Hab. Antedon phalangmm. The Minch. August 14, 1869. 
60 to 80 fathoms. 
This species has a very singular form. It is transversely oval, 
3*2 mm. wide and 2*7 mm. long; and it is thicker than any other 
free-living species. The dorsal surface is flat, while the ventral one 
is raised like a cushion, with the parapodia projecting round its edge 
at equal distances apart, as wide and blunt processes, at the points of 
which powerful booklets are protruded for some distance. There 
are no suckers ; while the mouth and cloacal openings, usually 
situated on the same side as the parapodia, are placed on the dorsal 
surface. Both this and the ventral surface are of a strong yellow 
brown colour. The only specimen obtained was closely attached to 
the perisome of its host. No other Myzostomida but M. pidvinar 
and M. alatum are known to infest Antedon plialangium. 
