REPORT ON THE OPHIUROIDEA. 207 



below, and, beyond the third plate, above also. Disk moderately thick, rising somewhat 

 above the arms, with a deep constriction in each interbrachial space. The area between 

 this constriction of the radial shields is occupied on either side by four or five transverse 

 plates running diagonally inward, whereof one or more are often broken in two. Central 

 disk somewhat sunken and covered with coarse, irregular, overlapping scales, which with 

 the larger plates and edge of disk, are closely beset with little cylinders bearing a crown 

 of thorns. Radial shields of an irregular pearseed-shape, with an angle inward, wavy, 

 scarcely sunken, very wide, separated by a broad wedge of scales forming a median hump 

 or ridge ; length to breadth, 3'7 : 2. Near base of arm, six rather stout, thorny, glassy, 

 blunt cylindrical arm spines, the lowest ones shortest and stoutest, but not curved ; 

 lengths to that of an arm joint, 3"3, 3'3, 2'1, 1"8, 1*8, 17 : 1'3. Beyond first pair of pores 

 the tentacle scales are cloven, or have a long point, with one or more side thorns ; 

 towards middle of arm these thorns become stronger and the scale more pointed. Colour 

 in alcohol, dull straw. 



A smaller specimen, with a disk of 8 mm., had arms about 65 mm. long. The disk 

 stumps were more thorny than in the larger one, and the tentacle scales, beyond middle 

 of arm, were short spines, with several sharp, slender side thorns. It is to be noticed that 

 the size and shape of the tentacle scale, when specimens of the same size are compared, 

 give a pretty constant character in O'pliiacantha and OjMomitra. 



Station 87.— July 21, 1873 ; lat. 25° 49' N., long. 20° 12' W. ; 1675 fathoms. 



Ophiomitra dipsacos, Lym. (PI. X. figs. 4-6). 



OpMomitra dipsacos, Lym., Bull. Mus. Comp. Zool., vol. v., part 7, p. 155, pi. viii. figs. 213-215, 

 1878. 



Upper arm spines long and slender, marginal disk plates large and swollen ; central 

 disk scales fine, and bearing minute thorny stumps ; arm wide. 



(Type specimen from Station 24.) Diameter of disk 10 mm. Width of arm without 

 spines 3 '4 mm. Mouth papillfe nine to eleven to each angle, whereof the innermost odd 

 one is flat spearhead-shape ; and the two outer ones on each side are ill-defined, being 

 sometimes small papillae, or again forming a sort of curled sheath to the mouth tentacle ; 

 the other papillae are pointed and flattened. Mouth shields as long as broad, small, 

 having an obtuse angle within, and a truncated angle or a deep curve without ; outer 

 edge often a little curled ; length to breadth, 2 : 2. Side mouth shields wide, with 

 outer side strongly curved. Under arm plates, near base of arm, large, much wider than 

 long, with an outer edge gently curved and slightly thickened, and reaching nearly 

 across the arm ; lateral sides re-enteringly curved, with a peak within, where each plate 

 is separated from its neighbour by the side arm plates. Upper arm plates slightly 

 swollen, bounded without by a gentle curve, and within by a deep curve or truncated 

 angle ; they are separated by side arm plates, which are prominent, and meet freely 



