244 ME. "VV. PEUCT SLADEN ON THE 



developing more or less of a knob. These expansions join at the 

 extremity of the ray, and form an arch over the termination of 

 the ambulacral furrow, the knobs bearing several prominent spine- 

 lets stouter than any of those in the vicinity. 



Ambulacral furrows broad and rather petaloid. Sucker-feet 

 arranged in simple pairs. Adambulacral plates very narrow and 

 spaced widely apart, the margin of the furrow being simply a 

 narrow ridge. Ambulacral spines normally two, placed trans- 

 versely and very slightly oblique ; but frequently only one is 

 present. They are long, thickened at the base, tapering to the 

 point ; and when two are present, the outer one is often much 

 larger than its companion. No trace of any investing mem- 

 brane. Squamous plates are present on the outer margin of the 

 adambulacral plates, which doubtless are the representatives of the 

 aperture-papillse. They seem to be more or less aborted func- 

 tionally in the specimen under notice, and are apparently auky- 

 losed, at any rate on the inner half of the ray, to the general body- 

 skeleton ; they are large, and broadly oval or subspatulate in shape. 



The mouth-plates resemble in character those of Hymenaster. 

 Median keel along suture very prominent adorally and sharply 

 rounded. Two short, robust, curved, slightly clavate, and rather 

 thorny spinelets stand on either side of the keel near the middle 

 of the plates. Owing to the bad state of preservation of this 

 specimen, the rest of the armature is unfortunately undistin- 

 guishable. 



Actino-lateral spines 15 to 20, or p erhaps rather more ; com- 

 paratively short, delicate, and widely spaced ; the longest about 

 fourth from the mouth, and rather shorter than the breadth of 

 the ambulacral furrow, measured from the base o£ this spine to 

 the base of its correspondent on the opposite side. The actino- 

 lateral spines do not diminish very rapidly in length as they 

 approach the extremity. A fibrillar tissue of very loose construc- 

 tion forms the web uniting the spines, and at the same time con- 

 stitutes the actinal floor of the test, beyond the margin of 

 which the spines project considerably. In places where the acti- 

 nal web has been removed in the interradial space, no papillae are 

 to be seen for supporting the pseudo-supradorsal membrane 

 from the sides of the rays, the cavity appearing to be very feebly 

 developed there. 



Station 244. Lat. 35° 22' N., long. 169° 53' E. Depth 

 2900 fms. ; bottom temperature 1°"2 C. ; red clay. 



