REPORT ON THE ASTEROIDEA. 607 



The disk is small and depressed, with the abactinal surface plane and at a higher level 

 than the base of the rays, the margin standing nearly vertical and being abruptly rounded 

 at the junction with the abactinal surface. The whole abactinal surface is covered with 

 minute, papilliform, skin-covered spinelets, all of uniform height, closely placed but dis- 

 tinctly spaced. The membrane which covers the abactinal surface of the rays is very 

 delicate and semitransparent. The inner portion of the ray, as far as the ovarial region 

 extends, is furnished with transverse annular ridges, about twenty-three or twenty-four in 

 number. The ridges, which are equidistantly spaced and are opposite to alternate adam- 

 bulacral plates, are very flexuous, and not unfrequently two neighbouring ridges on one 

 side of the ray may be joined by a longitudinal prolongation in the median radial line and 

 united to a single ridge on the opposite side of the ray, apparently corresponding to their 

 interspace. The ridges are very narrow and prominent, and are formed of minute imbri- 

 cating ossicles, which bear very small, isolated, conical spinelets, the prominence of the 

 ridges being greater and the spinelets much more widely spaced than in Brisi?iga endf- 

 cacnemos. The abactinal membrane between the ridges bears narrow saccular bands 

 crowded with minute pedicellarise, from one to three being present in each interspace. 

 These traverse the ray from side to side or may be interrupted and irregular, and fre- 

 quently conform to the flexure of the calcareous ridges. Minute spiniferous spicules are 

 also present on the membrane of the ovarial region, and are most numerous at the sides 

 of the ray and over the entire base between the disk and the ovarial inflation. Beyond 

 the ovarial region the abactinal membrane is extremely delicate, and the saccular bands, 

 which are broad and regular, are equally spaced and traverse the ray. 



The ambulacral furrow is wide and measures 3 "5 mm. at a part where the ray is 7'5 

 mm. (about 75 mm. from the disk). The adambulacral plates are longer than broad, 

 measuring about 2 mm. at 75 mm. from the disk, and the furrow margin of the plate is 

 rather deeply concave. The adambulacral armature consists of : — (1.) Two small spines on 

 the furrow margin, one attached near the adoral end of the plate, which measures about 2 

 mm., and the other near the aboral end, but being in the same line as the adoral spine is 

 consequently not at the extremity of the plate. This spine measures 3 "5 mm. Both these 

 spines are cylindrical, tapering, and covered with a delicate membrane bearing numerous 

 small pedicellarise. (2.) On the actinal surface of the plate is an elongate, delicate, taper- 

 ing spine measuring 8 to 9 mm., and invested with a membranous sheath, crowded with 

 minute pedicellarige, which develops a short saccular extension at the extremity. 



The lateral spine at about 75 mm. from the disk is also about the same length, 8 to 9 

 mm., or a shade longer. It is very delicate, and is similarly invested with a membranous 

 sheath crowded with minute pedicellaripe. It is articulated on the lowest plate of the 

 transverse annular ridge — a rudimentary infero-marginal plate — which is so intimately 

 united with the adambulacral plate as to appear like a tubercular eminence of that plate. 

 Further out on the ray the lateral spines are a little longer, but I have not found any 



