REPORT ON THE ASTEROIDEA. 639 
its extreme delicacy, and for this reason I am unable to say whether the pedicellariz 
were present to the same extent on the spinelets of the ovarial regions as on those of the 
disk. The plating does not terminate with the ovarial regions, but is continued along the 
ray, the plates, however, becoming much smaller and more delicate. I have traced it 
considerably beyond the middle of the ray, and isolated plates with single spines occur up 
to the extremity. It is only on the outer part that I have been able to find any traces of 
the groups of pedicellarize, comparable to those on the saddle-like sacculi, which are so 
conspicuous in other species. Certainly none are present where the plating is continuous. 
The groups here noted are circular in form, placed near the lateral margin of the ray, 
and the pedicellarize are extremely small. 
The ambulacral furrow is broad, and has a singular appearance, simulating rather 
suggestively a lineal series of confluent keyhole-shaped apertures, in consequence of the 
formation of the adambulacral plates about to be noticed. The adambulacral plates are 
elongate (2°5 mm. in length at 80 mm. from the disk), very like vertebree in form, with 
their furrow-margin deeply incurved. This scooping out of the margin does not commence : 
immediately at the adoral end of the plate, but rather abruptly a little way beyond; it 
is continued, however, up to the extreme aboral end, and the latter, in consequence of 
the depth of the concavity, has the appearance of being produced at an angle horizontally 
into the furrow; a keyhole-shaped outline is thus produced, and the width of the furrow 
is obviously much narrower when measured between the thick adoral portions of the 
adambulacral plates than across the deepest part of the incurvature, the breadth in one 
case being less than 1 mm., and in the other fully 2 mm., at a part where the width of 
the ray is 36 mm. The successive pairs of ambulacral tube-feet have thus a widely 
spaced and isolated appearance. The armature of the adambulacral plates is very simple, 
and consists of only one very delicate spinelet which stands perpendicularly, and an equally 
delicate lateral spine, articulated on a rudimentary ankylosed infero-marginal plate, usually 
on every alternate plate. The small imner spinelet at the aboral extremity of the furrow- 
margin of the plate, which is present in most species, is here wanting altogether. The 
perpendicular spinelet measures about 4 mm., but frequently less, and is articulated on a 
small tubercle situated on the actinal surface of the plate at its narrowest part, and con- 
sequently in a line with the pair of ambulacral tube-feet and nearer the aboral than the 
adoral extremity of the plate. It is encased in a delicate membranous sheath crowded 
with pedicellarize. The lateral spinelets are of very great delicacy, about 7 mm. in length 
at 150 mm. from the base, and like the perpendicular spinelets are encased in a delicate 
membranous sheath with crowded pedicellariz. So great is the delicacy of both perpen- 
dicular and lateral spines alike that very few can be found undamaged. 
The actinostome is wide, its diameter being 6°75 mm. in a disk measuring 12°5 mm. 
The buccal membrane is semitransparent and permits the plications of the digestive 
cavity to be seen. The mouth orifice is small, and its margin is much crenulated, the 
