REPORT ON THE ASTEROIDEA. 605 



inflated region only occupying about 23 mm. Beyond this the section of the ray is sub- 

 triangular with a truncate median carination. 



The disk is very small and depressed, with the abactinal surface subplane and nearly 

 on the same level as the base of the rays, the margin being slightly bevelled. The abac- 

 tinal area of the disk is covered with a delicate membrane, beset witli minute, papilliform, 

 skin-covered spinelets, all of uniform height and distinctly spaced. The membrane which 

 covers the abactinal surface of the rays is extremely delicate and quite transparent. The 

 inner portion of the ray, about one-third of the length, is furnished with from ten to twelve 

 transverse annular ridges, seven or eight of which are remarkably high and prominent in 

 relation to the size of the ray. The ridges are rather widely spaced, their distance apart 

 being equal to the length of two or three adambulacral plates, and they form a rigid 

 narrow crest, composed of small imbricating ossicles, Avhich bear small but robust conical 

 spinelets, rather widely and equidistantly spaced. One or more narrow transverse band- 

 like sacculi, crowded with minute pedicellarise, occur on the abactinal membrane in the 

 interspaces between the ridges, but no tegumentary spicules are present. Beyond the 

 ovarial region the abactinal membrane is extremely delicate and is occupied only by the 

 bands of pedicellarise. 



The ambulacral furrow is wide and occupies about 1 75 mm. at a part where the ray 

 is 3 mm. (about 50 mm. from the disk). The adambulacral plates are longer than broad, 

 measuring about T5 mm. at 50 mm. from the disk, and the furrow margin of the plate is 

 conspicuously concave. The adambulacral armature consists of: — (1.) Two small inner 

 spinelets directed horizontally over the furrow. (2.) A longer, more robust spine, standing 

 perpendicularly on the actinal surface of the plate. The lateral spine is borne on a small 

 rudimentary infero-marginal plate, so intimately united to the adambulacral plate as to 

 appear an integral part of it. The spine, which is remarkably delicate and needle-like, 

 measures 8 mm. at about 70 mm. from the disk, and is enveloped in an extremely thin 

 membrane with numerous pedicellariae. The actinal spine is shorter and even more deli- 

 cate, and is so fragile that I have been unable to find one unbroken near the reo-ion indi- 

 cated. Nearer the disk they measure 2 "5 to 3 mm. in length, and are invested with a 

 delicate membranous sheath bearing pedicellarise. The two small inner or furrow-spines 

 are equal, less than 1 mm. in length, and are invested with a delicate membrane expanded 

 into a slight sacculus at the tip and bearing a few pedicellariaj ; one is placed at each 

 extremity of the plate, and it thus follows that there are two small spinelets standing 

 parallel to one another between each consecutive ambulacral tube-foot. 



The actinostome is large and measures 8 mm. in diameter in a disk 13 mm. in diameter. 

 The mouth-plates are moderately large in comparison with the size of the disk, 

 and the united pair have a prominent median keel along the line of juncture, which is 

 imperfectly closed. Their armature consists of two small spines less than 1 mm. in length 

 on the adoral margin of each plate, the inner one, when directed horizontally over the 



