8 



which means that they are not yet full grown, even if they are as long as the 

 other spines (comp, the beautiful researches of Prouho). On the full grown 

 radioles the outer layer is covered with small, branched, bushshaped thorns, 

 arranged without order between the larger knobs or thorns; they may anastomose 

 with their branches: transverse sections of the spines give figures very much like 

 those of Unrocidaris papillata (Ingolf-Ech. PI. XI. Fig. 14, 31). 



The secondary spines have no ampulla; the ambulacral spines are much darker 

 than the interambulacral ones thus forming five dark, radiating lines on the animal. 

 On the actinal side they may be somewhat hollowed in the outer end (especially 

 those around the radioles), while those on the abactinal side are pointed. 



The spicules are of the form usual in Cidarids; they lie in two series, which 

 do not join on either side of the tube foot. In the lower part of the foot they are 

 smaller, less spinous and rather scarce. — The globiferous pedicellaria» have been 

 described and figured in the Ingolf-Echinoidea (p. 17. PI. X. Fig. 17). The tridentate 

 pedicellariæ (PI. IV. Fig. 30) do not present marked peculiarities; the valves are a 

 little apart below, when the pedicellaria is shut. — The walls of the intestine are 

 closely packed with small, smooth, mostly oval calcareous bodies with a few holes, 

 or with small, irregular, fenestrated plates (PI. V. Fig. 25). In the mesenteries, genital 

 organs, the organs of Stewart and along the radial ve.ssels irregularly shaped plates 

 are found (Pl.V. Fig. 20). 



A young specimen of 5 mm. in diameter shows the features pointed out by 

 DÖDERLEIN (Japanische Seeigel, p. 27 f.) as characteristic of young Cidarids; e-speci- 

 ally the obliquity of the pores is highly characteristic of the young as compared 

 with grown specimens (PI. II. Fig. 3.). In one thing this example differs from the 

 common rule, there being already a complete circle of small tubercles around the 

 aréoles, which are thus completely separated. Pedicellariæ are found already at 

 this size, the globiferous pedicellariæ are as yet small and not much lengthened, 

 all being of the small form; tridentate ones are numerous and of the typical form. 

 Spicules few and small. 



Of this species a good many specimens belonging to the forma typica of 

 DÖDERLEIN were taken on different places, at Koh Chuen and Koh Kram, between 

 Kob Rin and ClifT Rock, between Koh Kahdat and Koh Kut, in 10 — 30 fathoms, on 

 hard bottom. Also at Singapore a few small specimens were taken at 2— 3 fathoms. 



Two of the specimens were infested with Sty lifer; one of them especially 

 had many large individuals of this parasitic snail crowded on the apical area. 



