115 
Disk covered with a uniform coat of small spines or stumps 
generally ending in four short, diverging points. The scales of the 
disk are generally discernible, though with some difficulty (on the 
figure they are rather too distinet and the coat of spines not 
a. 
b. 
Fig. 7. Ophiacanthn vilis. a. Part ot 
ventral side, b. of dorsal side ; c. two 
armjoints, ventral side, from the middle 
of the arm. d. spine from the disk. 
a—c. d. 
dense enough), The radial shields not distinet, only just the outer 
end may be visible. On the underside of the disk the scaling is 
more distinet, the spine-covering less dense. — The oral papillæ 
are three to each side, the outer one generally scarcely widened; 
the infradental papilla is fairly large; rarely one may find in one 
of the' mouth angles the outer papilla represented by two mueh 
narrower ones, there being thus four papillæ here. The mouth 
shields are about equally long and broad, with a somewhat pro- 
duced outer lobe; the adoral shields crescent-shaped, meeting broadly 
within, but not produced outwards so as to separate the mouth 
shield from the first side armplate. The ventral plates are broader 
8 * 
