MUSEUM OF COMPARATIVE ZOOLOGY. 141 



minute thorns ; the upper one somewhat lon},'er ; lengths to that of an aim- 

 joint 4, 3, 2.8, l.G, 1.6, 1.6 : 1.2. One small, blunt, pointed tentacle-.scule. 

 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-papillae to an angle. 



Station 298, 2225 fathoms, 4 specimens. 



Ophiacantha stimulea sp. nov. 



Plate IX. Figs. 235-328. 



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-papillce, of which the two innermost are largest, the 

 others about equal. Teeth similar to innermost mouth-papillse, 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 pulled, 

 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. Tentacle-scales 

 long, pointed, and rather Avide ; two on each of first two or three pores, and 

 one on those beyond. Color in alcohol, white. 



Station 164, 950 fathoms, 1 specimen. 



This species is distinguished from 0. segesta by more numerous and different 

 mouth-papillte and by stouter arm-spines. 



Ophiacantha segesta sp. nov. 



Plate X. Fiff. 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 



