MUSEUM OF COMPARATIVE ZOOLOGY. 105 
Station 164, 950 fathoms, 1 specimen. Station 165, 2600 fathoms, 1 speci- 
men, Station 166, 275 fathoms, 1 specimen. Station 218, 1070 fathoms, 2 
specimens. 
OPHIOPLINTHUS * gen. nov. 
Disk smooth and covered by a thin skin bearing irregular delicate scales and 
radial shields, Genital scales wide and divided in several pieces. Small, 
blunt, close-set mouth-papille ; no tooth-papille ; short angular teeth ; very 
minute, peg-like arm-spines on outer edges of side arm-plates. Second pair of 
mouth-tentacles and first two pairs of arm-tentacles rising from round pores near 
the inner end of the under arm-plates ; those beyond are smaller, and stand 
close to the under arm-spine, Arms narrow, cylindrical, and gradually taper- 
ing. Two genital openings, running only a part of the way toward the margin. 
Mouth-frames seen from above, after removing the top of the disk, long and 
rising in a ridge, so that in the interbrachial space is a wide angle, and in the 
brachial space a deep trough. Arm-bones long and cylindrical, with only a 
faint upper furrow. Genital scales long, slender, and cylindrical. 
This genus by its large first under arm-plate has a slight relation to Ophio- 
glypha, and by its large tentacle-pores at base of arm, an appearance like Ophio- 
musium, but its structure is really quite peculiar. 
Ophioplinthus medusa sp. nov. 
Plate II. Figs. 30, 31, 40. 
Special Marks. — Scaling of lower interbrachial space coarse (four or five scales 
in a transverse row). No scales on arm-tentacles. Usually three very minute, 
peg-like arm-spines, equally spaced. 
Description of an Individual (Station 156),— Diameter of disk 16 mm. 
Width of arm 2 mm. Mouth-papille short, square, closely soldered, four or 
five on each side, with one, diamond-shaped, at apex of the jaw. Mouth-shields 
rounded triangular, with an angle inward, sides curved, and often a re-enter- 
ing curve without; they are frequently furrowed or cracked. Side mouth- 
shields irregularly rhomboidal, sometimes broader within, where they touch. 
First under arm-plate rounded triangular, with a blunt angle inward, and a long 
curved outer edge ; second plate five-sided, with an obtuse angle within, and a 
curved outer edge ; beyond this they are broader than long, with a blunt angle 
within and à wavy curve without. Side arm-plates thick and smooth, meeting 
broadly below and touching above beyond the sixth plate. Upper arm-plates 
rounded diamond-shaped, with a longer angle within ; they often are cracked 
or grooved. Disk high, covered with thin, irregular, overlapping plates ; the 
central p^^mary one about 2 mm. in diameter and conspicuously the largest, 
and in each brachial space is a primary plate larger than the rest. Radial 
shields irregular, four-sided, with rounded corners, broader on the outer edge, 
* Sis, snake ; mMv6os, tile. 
