MUSEUM OF COMPARATIVE ZOOLOGY, 117 
joint. The disk is rather flat, covered with microscopically tuberculated 
plates, well soldered together; the margin is occupied by one large plate, 
touching the radial shields on either side, and extending below to the mouth- 
shields ; the centre is occupied by six primary plates, one pentagonal, sur- 
rounded by five rudely hexagonal, "The radial shields are pear-seed shape, 
and large, having a blunt angle inward, and outer edge much rounded ; they 
touch only at their middle point, and are separated within and without by a 
small triangular scale. The interbrachial space below is covered by the large 
marginal plate, already mentioned, and the stout genital scales. Tentacle- 
scales minute, cireular, situated at the inner corners of the second and third 
plates. Two very small, short, and blunt arm-spines. Color in alcohol, white, 
Station 219, depth 150 fathoms, 1 specimen. 
Ophiomusium scalare sp. nov. 
Plate I. Figs. 1-3. 
Special Marks. — Most of the lower interbrachial space, outside the mouth- 
shield, is occupied by broad genital scales and a great central plate. No under 
arm-plates beyond the third, Three short, stout, well-defined arm-spines. 
Disk-plates thick, separated by narrow grooves, and arranged above like steps, 
Side arm-plates flaring a little outward. 
Description of an Individual (Station 171). — Diameter of disk 5 mm. 
Width of arm without spines 1 mm. Length of arm about 10 mm. Mouth- 
papillae three on each side, and one at angle of jaw, closely soldered together, 
forming high continuous ridges, radiating from the mouth. Mouth-shields 
five-sided, having a long acute angle within, and the outer side straight ; 
length to breaath 1: 1. Side mouth-shields long, narrow, meeting within ; 
broader without than within, where they join the first side arm-plate ; length. 
1 mm. Genital scales large semicircular, somewhat swollen. Under arm- 
plates minute, three in number; the first one semicircular, wedged between 
the side mouth-shields ; second and third longer than wide, with acute angle 
inward, lateral sides straight, and outer side slightly curved. Tentacle-scales 
round, very small, situated near inner angle of the under arm-plate, Side 
arm-plates thick, swollen, covering almost the entire arm beyond the disk. 
Upper arm-plates minute, diamond-shaped. Under surface of disk covered, in 
the interbrachial spaces, by genital scales, and three large swollen semicircular 
plates, whose outer edge is curved; upper surface of disk covered with small 
tuberculous plates, forming a much raised rosette, the central plate of which 
is pentagonal, the primary plates surrounding it semicircular, Radial shields 
closely soldered together, and partly separated by an angular plate. In the in- 
terbrachial spaces are two large plates, radiating from the central rosette, one 
five-sided, with an acute angle inward, and joined to the inner edge of the 
radial shields ; the other, which is on the margin of the disk, is a large, nearly 
square, corrugated plate, and is attached on either side to small oval plates, 
