MUSEUM OF COMPARATIVE ZOOLOGY. 141 
minute thorns ; the upper one somewhat longer ; lengths to that of an arm- 
joint 4, 3, 2.8, 1.6, 1.6, 1.6: 1.2. One small, blunt, pointed tentacle-scale. 
Color in alcohol, disk above dull chocolate-brown, lower side and arms pale 
brown. 
The only essential variation noted was in a larger specimen, with a disk of 
18 mm., which had sometimes as few as seven mouth-papille to an angle. 
Station 298, 2225 fathoms, 4 specimens. 
Ophiacantha stimulea sp. nov. 
Plate IX. Figs. 225 -228. 
Special Marks. — Disk closely set with small simple spines. Arm-spines not 
thorny. One or two large long tentacle-scales, 
Description of an Individual (Station 164). — Diameter of disk 7 mm. Length 
of arm 35 mm. Width of arm without spines 2 mm, Ten or twelve pointed, 
flat, rather thin mouth-papille, of which the two innermost are largest, the 
others about equal. Teeth similar to innermost mouth-papille, but larger. 
Mouth-shields wider than long, rather small, bounded without by a curve and 
within by an obtuse angle. Side mouth-shields somewhat curved, rather 
narrow within, where they meet, wide without. Under arm-plates wider with- 
out, where they are bounded by a gentle curve, than within, where they pre- 
sent an obtuse angle ; lateral sides slightly re-enteringly curved. Upper arm- 
plates fan-shaped, with an angle inward. Side arm-plates stout and prominent, 
meeting narrowly above and below, near base of arm. Disk a little puffed, 
with a constriction in each interbrachial margin, closely set with small simple 
spines, which, under the microscope, are seen to be slightly rough at their tips; 
just over each arm they are much shorter, and extend to the first upper arm- 
plate. Radial shields and scaling wholly obscured by thick skin and spines, 
except on a small patch next mouth-shields, Seven regular, not thorny, nearly 
cylindrical, rather slender arm-spines, which taper slowly to a blunt point ; 
lengths to that of an arm-joint 2, 3, 2, 1.5, 1.5, 1.5, 1:.8.  Tentaele-scales 
long, pointed, and rather wide; two on each of first two or three pores, and 
one on those beyond. Color in aleohol, white. 
Btation 164, 950 fathoms, 1 specimen. 
This species is distinguished from O. segesta by more numerous and different 
mouth-papille and by stouter arm-spines. 
Ophiacantha segesta sp. nov. 
Plate X. Fig. 271. 
Special Marks. — Disk beset with short, smooth, slender spines, mingled with 
minute thorny stumps ; arm-spines not thorny. 
Description of an Individual (Station 56), — Diameter of disk 3.5 mm. Length 
