MUSEUM OF COMPARATIVE ZOOLOGY, 143 
large part of their length, long, narrow, joined, raised above surrounding surface ; 
scaling hidden. Five or six essentially smooth, tapering, and nearly equal arm- 
spines, of which, however, the upper one is much the stoutest,; lengths to that 
of an arm-joint 1.8, 1.6, 1.5, 1.5, 1.5: 1.2, or 2.2, 1.6, 1.5, 1.8, 1.3, 1 
Tentacle-scales flat, pointed, and rather small. Color in alcohol, pale brown. 
The species stands near the typical O. setosa in respect to form of disk and 
length of arm ; but it differs from this and most others of the genus in having 
naked radial shields and side arm-plates, which do not project to give a knotted 
look to the arm. 
Station 33, off Bermudas, 300 fathoms, 1 specimen. Two specimens from 
the “Blake” expedition, dredged in«101 fathoms by A. Agassiz, showed no 
important variations, The disk-grains were larger and more numerous, 
Ophiacantha cuspidata sp. nov. 
Plate X. Figs. 248 - 250. 
Special Marks. — Disk beset with thorny stumps ; eight rather long, stout, 
and feebly thorny arm-spines : about eleven long slender mouth-papillo. 
Description of an Individual (Station 344). — Diameter of disk 9 mm. Length 
of arm 63 mm. Width of arm without spines 3 mm. Ten or sometimes eleven 
long, flat, rather slender and irregular mouth-papilla, of which the outer one 
has often a spatula shape. Teeth long, spearhead-shaped. Mouth-shields 
small, long pentagonal, with a wide obtuse angle within ; length to breadth 1 : 1. 
Side mouth-shields small, narrow, and crowded, meeting within. Under arm- 
plates wider without than within, where they touch the next plate ; bounded 
without by a rounded angle or a somewhat deep curve, within by a more gentle 
curve, and on the lateral sides, opposite tentacle-scales, by re-entering curves, 
The second plate is narrower within, and has a wavy outer edge. Upper arm- 
plates fan-shaped, with an angle inwards ; the lateral corners are sharp, and 
the lateral sides slightly re-enteringly curved. Side arm-plates moderately 
prominent, meeting narrowly above, but not below at base of arm. Disk 
moderately thick, not puffed, closely set with stout little stumps each bearing 
a crown of five or six minute thorns. Radial shields and disk-scales hidden 
by skin and the thorny stumps, except that the position of each radial shield 
is usually marked by a shallow furrow. Eight stout, long cylindrical arm- 
spines, tapering to a blunt point and set with fine thorns ; lengths to that of an 
arm-joint 3.6, 5, 3, 2, 2, 2, 1.8, 14:1. On first pore two tentacle-scales ; on 
the rest a single large pointed scale, Color in alcohol, dark straw. 
A young specimen with a disk of only 1.5 mm. had an arm of 10 mm. The 
disk armature was little crochets with two or three prongs ; the arm-joints 
were of course more constricted, and the upper and under arm-plates were 
widely separated ; there were four or five arm-spines, whereof the first or 
second was much the longest ; to each mouth-angle seven papilla, whereof the 
lateral were bead-like and had not yet become long and slender, 
Station 344, 430 fathoms, 12 + and 5 young specimens. 
