636 THE VOYAGE OF H.M.S. CHALLENGER. 



and the surface presents a finely papillate appearance. A few comparatively large isolated 

 pedicellarise are present here and there on the general membrane amongst the spinelets. On 

 the outer part of the ovarial region the spinelets cease and their place is taken by pedicel- 

 larire. Beyond this region the ray is covered with a delicate semitransparent membrane, 

 upon which transverse saddle-like saccular bands are borne, crowded with very minute 

 pedicellarise. The bands extend from one margin of the ray to the other, and are broad 

 and uninterrupted across the median keel of the ray. The breadth of the bands is normally 

 greater than that of the interspaces ; they are usually more or less expanded near the 

 margin, and frequently the band there is bent sharply at a right angle and may be pro- 

 longed so as to merge into the next succeeding band, and sometimes quite a series are 

 thus united by a longitudinal band running parallel to the margin, especially on the 

 proximal part of the ray. The bands, normally correspond to the ambulacral segments of 

 the ray and usually cross the " vertebrae," as seen in the median keel, between the adoral 

 and aboral extremities ; their position, however, in this respect is not constant by any 

 means, as they may cross at all intermediate positions, and sometimes pass over the suture 

 uniting two succeeding "vertebra?;" sometimes two succeeding bands are united by a 

 longitudinal prolongation close to the keel, and sometimes a band commencing at one 

 margin of the ray crosses the keel, and then stops abruptly, leaving the other side of the 

 segment without a sacculus. 



The ambulacral furrow is of great width, and measures 3'5 mm. at a place where the 

 ray is 57 mm. (53 mm. from the disk). The adambulacral plates are slightly longer than 

 broad, measuring 175 mm. at about 53 mm. from the disk, and they form a narrow 

 margin to the furrow. The furrow-margin of the plate is slightly incurved. The adam- 

 bulacral armature consists of : — (1.) a small inner spinelet directed horizontally over the 

 furrow ; (2.) an elongate spine articulated on the actinal surface of the plate and standing 

 perpendicularly or directed outwards ; and (3.) a lateral spine of great length and delicacy 

 borne on alternate plates only. The small inner spine is attached to the extreme aboral 

 end of the furrow-margin of the plate and lies quite within the furrow, across which it is 

 directed horizontally and slightly forwards ; it is about 2 mm. in length, and is of a 

 remarkable shape, being flaring and fan-bke in form, and covered with a delicate, semi- 

 transparent membrane, more or less saccular, and upon which three or four large isolated 

 pedicellarise are borne. The plane of the flattened surface is vertical and perpendicular 

 to the axis of the ray. The actinal spines are about 7 mm. in length at 50 mm. from the 

 disk, and are articulated on a tubercle situated on the actinal surface of the plate close to 

 its aboral end ; they are encased in a delicate, semitransparent membranous sheath crowded 

 with great numbers of very minute pedicellarise, and with a saccular prolongation at the 

 tip. On the inner part of the ray, for about 40 mm. from the disk, these spines are 

 slightly expanded at the tip, but still remain cylindrical, and are truncate and often 

 calicular ; the membranous sheath does not cover this flaring tip, but terminates beneath 



