REPORT ON THE OPHIUROIDEA. 197 



1 : 1 - 3. Side mouth shields rather narrow, of nearly equal width, meeting within. Under 

 arm plates wider than long, with a slight peak within, and the outer side (especially a little 

 way out on arm) very strongly curved. Upper arm plates very small, sunken below the 

 ridge of side arm plate, of a rounded fan shape, with an angle inward. Side arm plates 

 large, meeting broadly above and below, with a spine ridge which swells gradually from 

 the plate, and does not form a steep narrow crest. Disk densely beset with very fine, 

 thorny stumps. Eadial shields and scaling hidden. Seven long, slender, translucent arm 

 spines, essentially smooth, only the lower ones being slightly rough under the microscope. 

 Lengths to that of an arm joint, 3'5, 3'5, 3"5, 2 - 8, 1'8, 1"3, '8 : "8. Tentacle scales 

 narrow and sharp. Colour in alcohol, white. 



The great size of the side arm plates and the number and length of the arm spines 

 mark this as an immature specimen, but the specific characters are not found in any 

 other. 



Station 214.— February 10, 1875 ; lat. 4° 33' N., long 127° 6' E. ; 500 fathoms ; 

 globigerina ooze. 



Ojyhiacantha serrata, Lym. (PI. XV. figs. 6-8). 



Ophiacantha serrata, Lym., Bull. Mm Comp. Zool., vol. v., pt. 7, p. 148, pi. x. figs. 272, 273, 1878. 



Disk closely and evenly set w T ith minute grain-like stumps bearing a crown of blunt 

 thorns ; arm spines long, slender, strongly thorny, translucent, mounted on steep, narrow, 

 much projecting side arm plates. 



(Type specimen from Station 219.) Diameter of disk 6 mm. Length of arm about 

 32 mm. Width of arm without spines l - 8 mm. Seven flat, rather blunt mouth papillae, 

 not crowded ; the innermost one much the largest and squarish ; besides these, the first 

 under arm plate bears two tentacle scales, one to each of second pair of mouth tentacles. 

 Four flat teeth, similar in shape to the innermost mouth papillEe. Mouth shields much 

 wider than long, of a transverse diamond shape, with lobe-like angles. Side mouth shields 

 straight and narrow, nearly or quite meeting within. First under arm plate small and 

 rounded, and bearing on its inner edge two tentacle scales ; second plate long axe-shaped, 

 with a curve without, a well marked angle within, and lateral sides re-enteringly curved ; 

 third plate proportionately shorter and with the inner side a very obtuse angle. Upper 

 arm plates small, of a wide fan-shape, with the angle inward. Side arm plates large 

 meeting widely .above and below, rising very suddenly to form a high, narrow spine ridge, 

 so that the arm has the look of a series of short cylinders alternating with burrs 

 Disk densely and evenly beset with minute grain-like stumps, bearing a crown of blunt 

 thorns. Scaling and radial shields covered, except outer tips of the latter. Nine long, 

 slender, translucent, strongly thorny arm spines ; lengths to that of an arm joint, 4, 4, 4, 

 3"2, 27, 2 - 5, 1*8, 1"8, 1*3 : 1. One small spiniform tentacle scale. Colour in alcohol, 

 white mottled with pale brown. 



(zool. chall. exp. — part xiv. — 1882.) 26 



