BULLETIN OF THE 
OPHIOCHITON * gen. nov. 
Disk covered with fine, imbricated scales and small radial shields. Numerous 
sharp mouth-papillie, with teeth but no tooth-papille, Upper and under arm- 
plates about as broad as long, and separating the side arm-plates, which project 
slightly and are rather small. Under plates furnished with a median longi- 
tudinal ridge, Arm-spines slender and smooth, arranged on the sides of the 
side arm-plates, near the outer edge. Two long genital openings in each 
interbrachial space. 
The genus is allied to the true Ophiarachna, which, however, has a granulated 
disk. 
Ophiochiton fastigatus sp. nov. 
Plate VII. Figs. 182, 183. 
Special Marks. — Four slender, smooth, tapering, blunt arm-spines. Scaling 
of disk very fine, with a few larger rounded plates. Radial shields small and 
separated. About thirteen mouth-papille to each angle. 
Description of an Individual (Station 232). — Diameter of disk 20 mm. 
Width of arm, without spines, elose to the disk 2.8 mm. Five or six sharp 
pointed papille on each side of an angle, and one shorter and more rounded 
at the.apex.  Mouth-shields much broader than long, with lateral corners 
rounded, a peak within and a lobe without; length to breadth 2.3 : 3. Side 
mouth-shields very narrow, broader without than within, where they meet. 
First under arm-plate very small, triangular ; the other plates are four-sided, 
with outer and inner edges nearly straight, and deep re-entering curves on the 
lateral sides: they are highly arched, forming along the arm a longitudinal 
ridge. Side arm-plates small, with a rather low spine-ridge, not meeting 
below or above. Upper arm-plates broader than long, slightly arched, four- 
sided, broader without than within ; inner and lateral sides straight, outer edge 
slightly curved. Disk flat, with interbrachial spaces somewhat contracted, 
covered above and below by very minute, thin, overlapping scales ; three to 
five in the length of a mm. and somewhat larger near margin. In each brachial 
space there is a’ row of small rounded scattered plates, radiating from the 
central primary plate ; genital scales covered, Radial shields widely separated, 
long triangular, and small, with an angle within ; length to breadth 2 : 1. 
Four smooth, tapering, blunt, nearly cylindrical arm-spines, placed high on the 
sides of side arm-plates near the outer edge; lengths to that of an arm-joint 
1.8, 1.8, 1.8, 2: 1.8. Two tentacle-scales on each pore, one large one on 
the interbrachial and a smaller one on the brachial side. Color in alcohol, 
pale brown ; upper disk inclining to olive, 
A smaller specimen with a disk of 12 mm. had arm 70 mm. long. It was 
similar to the adult, except that there usually were but three arm-spines, and 
* pus, snake ; xurwy, coat of mail. 
