95 



and 4 intermediate ones. The largest are those at each side of the primary tubercle; 

 from there the depressions decrease in size towards the angles. Outside the large 

 grooves there is only one, the angular gi-oove, inside the large ones there are two 

 intermediate grooves and the angular one. Towards the apical system the grooves 

 nearest the angular ones by and by disappear, uniting with the angular ones. On 

 the 4 — 5 uppermost plates there are only two grooves in each horizontal suture; 

 from the 5"' — 6"^ the two large grooves at the primary tubercle become separated 

 off from the angular ones. Below the ambitus all the intermediate grooves dis- 

 appear very soon, whereas the angular ones may be traced almost to the peristome. 

 The inner angular groove is continued over the suture upon the median corner of 

 the opposite plate. 



The apical area, 85 mm. in diameter, is regular, no ocular plate reaching 

 the periproct. The genital opening is at the outer edge of the plate, and there is 

 a small genital papilla. A circle of tubercles is found at the inner edge of the 

 genital plates. The ocular plates are covered by numerous small tubercles. The 

 anal area (45 mm.) is covered by numerous small, irregular plates without tubercles. 

 No distinct anal plate. The anal opening is central. 



The buccal membrane has only some few small plates in the inner edge 

 besides the buccal plates, which are equally distant from the edge. Otherwise the 

 buccal membrane contains numerous slender, biliamate spicules, which are often 

 arranged in thick bundles, mostly forming rings (PI. V. Fig. 21). — The spines are 

 very short, the longest being scarcely 5 mm., Ve of the diameter of test. They are 

 greenish, dark at the base and faintly ringed; they are smooth, ending in a rather 

 large central thorn with a circle of small thorns at its base ; the point is not swollen. 

 The actinal ones are a little widened, flat and curved. 



The globiferous pedicellariæ (PI. VII. Figs. 18, 19) have no lateral teeth, but 

 a rather large rounded knob on each side below the endtooth; the blade is rather 

 elongate, the outer corners of the basal part rounded, not produced. Tridentate 

 pedicellariæ occur in this species (PI. VI. Fig. 42. PI. VII. Fig. 45); they are rather 

 small (c. 05 mm. head). The valves are broad, with a little meshwork at the bottom 

 of the blade. The edge has some coarse sinua lions in the outer part and is other- 

 wise finely serrate in the whole length. The valves join in their whole length. 

 Below the basal part there is a well developed semicircular arc, as in the ophice- 

 phalous pedicellariæ, a very interesting, though not unique, feature. The ophice- 

 phalous pedicellariæ are like those of 0. variabilis; the triphyllous ones (PI. VII. 

 Fig. 27) have the blade somewhat widened. — Bihamate spicules are found in the 

 tube feet, though not very numerous, and at the base of the spines. — The colour 

 of the test is greenish-gray, with large, irregular spots at the ambitus; the actinal 

 surface is white. 



The only specimen known of this most interesting species was taken by 

 the „Challenger- at the Kei-Islaniis (New Guinea), Lai. 5" 42' S., long. 132 25' E. 



