REPORT ON THE ASTEROIDEA. 600 



Rays very long and attenuate, but of a comparatively robust habit in proportion to the 

 small size of the disk, when compared with other species of the genus, narrow and cylindrical 

 at the base, but gradually swelling into an elongate fusiform ovarial inflation, which 

 contracts gradually and terminates at 45 to 48 mm. from the disk, thus occupying about 

 the proximal fifth of the length. Beyond the ovarial inflation the ray is subtriangular, 

 with a broad median carination, and tapers gradually to the extremity. 



The disk is small and subdepressed, with the abactiual surface subplane and on the 

 s;ime level as the base of the rays or even slightly lower. The abactiual su rface is covered 

 with an exceedingly delicate semitransparent membrane, beset with very minute micro- 

 scopic spinelets, each borne on a small subcircular spicule-like plate buried in the membrane 

 and widely spaced. No definite order of arrangement is distinguishable amongst these 

 spiniferous spicules, and the delicacy of the abactiual membrane is so great that traces 

 of the internal organs may be seen through the interspaces. The membrane which covers 

 the abactiual surface of the rays is even more delicate than that of the disk. The inner 

 portion of the ray, as far as the ovarial region extends, is furnished with transverse 

 annular ridges, similar to those in Brisinga endecacnenios. These are very narrow, often 

 irregular, and more or less flexuous, and their normal position appears to be opposite 

 alternate adambulacral plates, but this is not invariable. A few isolated spicules may 

 be found in the intermediate spaces, and saccular bands crowded with small pedicellarige 

 are present, but from the condition in which the specimen now is, I am unable to remark 

 on their character or dimensions, but where preserved the}' appear to be broad continuous 

 bands extending from marsfin to margin. The transverse keels or ridges are formed of a 

 number of small ossicles imbricating on one another and bearing minute, isolated, short, 

 thorn-like spinelets. Beyond the ovarial region the abactiual membrane was of great 

 delicacy, and where present may be seen to form transverse folds or plications, but owiug 

 to its delicacy it is wanting on the greater portion of the ray. 



The ambulacral furrow is wide and measures 2 "7 5 mm. at a part where the ray is 

 4 - 5 mm. (about 70 mm. from the disk). The adambulacral plates are longer than broad, 

 measuring 2 mm. at 70 mm. from the disk, and the furrow-margin of the plate is deeply 

 concave. The adambulacral armature consists of: — (1.) two small inner spinelets, directed 

 horizontally over the furrow ; (2.) a longer and more robust spine standing perpendicularly 

 on the actinal surface of the plate; and (3.) a still longer lateral spine, usually borne on 

 every third plate, i.e., with two unarmed plates between, but sometimes there is only 

 one. The two small inner spines are attached, one near the adoral and the other near 

 the aboral end of the furrow-margin of the plate, and are directed horizontally over the 

 furrow at a right angle to the margin. It thus follows that there are two small spinelets 

 between each consecutive ambulacral tube-foot. These spines are of equal size, less than 

 1 mm. in length, cylindrical, and covered with extremely delicate membrane, on which 

 are borne a few comparatively large pedicellarige. The actinal spine is articulated on a 



(ZOOL. CHALL. ESP. — PART LI. 1888.) 77 



