MUSEUM OF COMPARATIVE ZOOLOGY. 111 
Width of arm, without spines, close to disk 2 mm. — Mouth-papilla seven on 
each side, three basal ones considerably largest ; all forming a close line. 
Mouth-shields small, triangular, with acute angle inward, and outer edge much 
rounded. Side mouth-shields large, much longer than broad, wider without, 
meeting within ; length to breadth 1.7 : 1. Under arm-plates from the second 
to the fourth or fifth furnished with tentacles; they are axe-shaped, with an 
angle inward, lateral sides re-enteringly curved and outer side curved ; beyond, 
the plates are rudimentary and diamond-shaped. Side arm-plates thick, meet- 
ing above and below beyond the disk. Upper arm-plates diamond-shaped, 
with an angle without and within ; length to breadth .7 :.7. Genital scales 
long and narrow, bearing a row of papillo on the free edge. Lower inter- 
brachial space covered by thin curved plates, of which five form a transverse 
row along the disk margin ; upper surface of disk pentagonal. Radial shields 
triangular, separated their entire length by a row of small plates ; and there 
is a similar row in each interbrachial space ; the central space within the 
radial shields is covered by six circular primary plates separated by small 
ones, Arm-spines six or seven in number, very short and blunt, situated on 
the outer edge of the side arm-plate. No scales beyond the fourth or fifth 
under arm-plate : they are large, oval, and situated near the inner angle of the 
plate, one to each pore. Color in alcohol, gray. 
Station 224, 1850 fathoms, 3 specimens. 
Ophiomusium cancellatum sp. nov. 
Plate I. Figs. 17, 18. 
Special Marks. — Arms rather slender and tapering, cylindrical or but 
slightly wavy. Upper and under arm-plates persisting nearly to end of arm, 
but no tentacles beyond third or fourth under plate, Genital openings bounded 
by small close-set papillw. Disk flat, covered with small imbricated scales, 
which are nearly equal, except the marginal, which are larger. Upper arm- 
plates large ; the basal ones long hexagonal. 
Description of an Individual (Station 236). — Diameter of disk 8.5 mm. 
Width of arm, without spines, 1.5 mm. Length of arm 28 mm. Mouth- 
papilla forming a close line, six on each side, with one, diamond-shaped, at 
angle of jaw. Month-shields triangular, with an angle inward, sides equal 
and curved; length to breadth 1:1. Side mouth-shields long triangular ; 
much wider without than within, where they do not quite meet. Genital 
scales concealed under fine, closely set disk-scales. Under arm-plates pentagonal 
near base of arm, farther out quadrangular, with an angle inward ; one tenta- 
cle-seale, which is round, and situated on inner angle of the second and third 
under arm-plates. Side arm-plates thick, minutely tuberculous, meeting be- 
low, but not above, near base of arm. Upper arm-plates near base of arm 
hexagonal, with outer and inner sides very short. Disk covered above and 
below by thin, rounded, minutely tuberculous scales ; on the margin are larger 
