REPORT ON THE OPHIUROIDEA. 189 



Oiohiacantha segesta, luym. (PI. XV. figs. 1, 2). 



OpMacantha segesta, Lym., Bull. Mus. Comp. ZooL, vol. v., part 7, p. 141, pi. x. fig. 271, 1878. 



Disk beset with sliort, smooth, slender spines, mingled with minute thorny stumps ; 

 arm spines not thorny. 



{Type specimen from Station 56.) Diameter of disk 3'5 mm. Length of arm 15 mm. 

 Width of arm without spines 1 mm. Seven regular, sharp, conical mouth papillae to each 

 angle, whereof the innermost is much the largest, and resembles the teeth, which are stout, 

 blunt, spearhead-shaped. Mouth shields small, wider than long, with a point within and 

 a curve without. Side mouth shields wide, thick, and somewhat curved. Under arm 

 plates thick and swollen, pentagonal, with an angle inward and outer side widest. Upper 

 arm plates thick and swollen, short fan-shaped, with an angle inward. Side arm plates 

 large, meeting widely above and below, swelling gradually to form the spine ridges, 

 which are not narrow or abrupt. Disk thickly set with small, slender, smooth spines, 

 among which appear minute thorny stumps and crochets. Scaling and radial shields 

 hidden, except outer tips of the latter. Seven smooth, tapering, cylindrical arm 

 spines near base of arm, of which the two upper ones are much the longest, attaining a 

 length of 1*7 mm. ; the lower ones are short and stout. At tip of arm the lowest spine 

 is slender, a little curved, and slightly rough on its edge. One small pointed tentacle 

 scale. Colour in alcohol, white. 



A young and immature specimen, Init distinctly characterised by its spiny disk. 



Station 56. — May 29, 1873 ; off Bermudas ; 1075 fathoms; grey ooze. 



Ophiacantha ahnormis, Lym. (PL XXVL figs. 4-6). 



Ophiacanfha ahnormis, Lym., BuU. Mus. Comp. Zool., vol. vi., part 2, p. 59, pi. xv. figs. 

 411-413, 1879. 



]\Iouth angles elongated, bearing, towards the apex, twelve or fourteen slender, pointed 

 papillae. Six long, smooth, slender arm spines. Disk sparsely set with very short spines. 



(Type specimen from Station 207.) Diameter of disk 11 mm. Length of arm, which 

 is very attenuated near its end, 73 mm. Width of arm close to disk, without spines, 

 2 "5 mm. • Mouth angles elongated, having no papillae on their outer part near the mouth 

 tentacles, but on their inner portion bearing four or five slender, spaced papillae on each 

 side, and a cluster of three or four at the apex. Teeth wide and large, with a broad 

 cutting edge. Mouth shields broad triangular, with a small peak on the outer edge, 

 and blunt angle within. Side mouth shields short and extremely narrow, just meeting 

 within. Under arm plates thin and sunken, pentagonal, with a Inroad angle inward, 

 outer edge straight, and deep re-entering curves on the lateral sides. Beyond the thii-d, 

 they are separated by the side arm plates, which meet below and above and have a high 

 wide spine ridge. Upper arm plates triangular, somewhat swollen, with an angle inward, 



(zool. CHALIi. EXP. PART XIV. — 1882.) O 25 



