592 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
are therefore taken from Hartmeyer (1903) and are not based on 
American specimens. 
Body much flattened ; surface with eight horny plates (seven margi- 
nal, one central) besides six surrounding each siphon. 
Tentacles of several sizes, over 100 in number. 
Dorsal tubercle crescent-shaped, horns not spirally inrolled, open 
interval directed forward. 
Dorsal lamina with sickle-shaped languets. 
Stigmata curved; internal longitudinal vessels present. 
Intestine ventral and on the left side; loop broad; stomach with 
diverticula. 
Reproductive organs spreading in a net-like manner over the in- 
testinal loop. 
Stimpson's (1852) description is as follows: 
" Body adhering by a broad base, depressed, oval. Test thin, smooth, 
transparent, very pale greenish, with an almost peripheric, narrow, 
dark-colored line or ridge, like a fibre, from which other lines of the 
same character proceed, dividing the surface into ten irregular polygons, 
two of which, separated from each other by a third, contain the aper- 
tures. These two polygons are wheel-like, being radiated with six 
spokes from a centre, which is the sessile aperture. Proceeding from, 
and perpendicular to each of the dark lines, are bright straw-colored 
fibres, extending toward the centres of the polygons but not reaching 
them. Length, half an inch. 
"Dredged in forty fathoms on a muddy bottom off Long Island, 
Gr. Manan. One specimen only was found, which was adhering to 
a dead valve of Pecten Magelkmicus." 
According to Redikorzew (1908b, p. 40) this species is known from 
Norway, Spitzbergen, Murman Coast, White Sea, Siberian Arctic 
Ocean, the northern North Pacific, Greenland, Jan May en, and Ice- 
land. Apparently it is nowhere common. It inhabits stony or 
muddy bottoms when containing also stones, in depths from 10 to 
99 meters. 
On the American coast it was collected by Stimpson (1852) near 
Grand Manan as above stated, and by Verrill (1873) in Casco Bay, 
Maine (off Witch Rock, 18 fathoms, stony). It is evidently exceed- 
ingly rare, and confined to the northern part of the region. 
