320 



DISCOVERY REPORTS 



usually somewhat more prominent. These ventral plates have no elevated knob, but 

 usually show a fairly distinct concentric striation. The buccal plates are small, oval, 

 more or less irregular, sometimes with the proximal part separated off as a distinct small 

 plate. Adoral plates and jaws elongate, oval. Mouth papillae of the usual square shape. 

 First ventral plate large, with a rounded inner edge and a nearly straight outer edge. 

 It is distinctly separated from the second ventral plate ; also all the following ventral plates 

 are separated. They have a rather sharp angle proximally, the distal edge being lightly 

 convex or a little produced in the middle. The proximal part of each joint on the ventral 

 side in larger specimens sunken, the distal part correspondingly raised, giving a some- 

 what ladder-like appearance. The dorsal arm plates about hexagonal, contiguous, each 

 plate rising into a rather sharp central knob, or there may be two or three serrations on 

 the top. The arms on the whole conspicuously keeled, triangular in section. Usually 

 two rather sharp, often somewhat outstanding arm spines, the lower one placed close 

 to the two spine-like tentacle scales, the upper one a little distance above. The genital 

 slits are very short, not extending beyond the end of the first lateral plate ; the interradial 

 side of the slit carries about four well-developed, square papillae, the adradial edge 

 is raised into a sharp keel, without indication of papillae. In continuation of the genital 

 slit there are a varying number of small spine-like granules which continue along the 

 sides of the arms to the dorsal side along the distal edge of the radial shields, forming 

 thus a rudimentary arm comb. Colour in alcohol whitish. 



All the specimens are covered with a thick, irregular layer of a sponge, which, 

 according to the kind information of Mr Burton, is the same species as that which so 

 often covers Ophiiirolepis gelida} It often covers the Ophiuran completely, both dorsal 



and ventral side of both disk < ^x ^_-_s;Hr-=:^\ 



and arms, leaving only the 

 mouth and the bursal slits 

 uncovered. 



Like O. gelida this species 

 has separate sexes and is evi- 

 dently not viviparous. The 

 gonads are arranged in the 

 same way as in O. gelida; the 

 eggs are about the same size as 

 in the latter, and also ripen all 

 at the same time. 



It is clear that this species is 

 closely related to O. gelida, but Fig. 38. Part of arm, in side view, of Ophiiirolepis gelida (a) 

 is well distinguished from the ^"'^ ^- brevirima (b~c); b is from a younger specimen, xg. 

 latter, particularly by its peculiar short genital slits. The shape of the dorsal plates is 

 also a little different ; but more important is the fact that the ventral plates are separated 



1 This is generally stated to be lophon flabelli-digitalus, Kirkpatrick. Mr Burton informs me that it is 

 lophon radiatus, Topsent. 



