ECHINOIDEA. I. 



39 



In a quite young specimen, of a diameter of 7""", with oiily 4—5 interambulacral jDlates, as \et 

 almost 110 small tubercles (and spines) are found, excepting the primary series in the ambulacral areas, 

 and the circle roimd the areoles (which are not yet deepened). Nevertheless no naked spots are seen 

 on the test — there is no space for more tubercles. The apical area is closely set with small 

 tubercles. There are as yet only 5 piates in the periproct, in the corners between the genital piates 

 (which have not yet any genital opening). Round the anal opening there is a circle of small 

 tubercles. 



The spines are highl}- characteristic (PI. VI. Figs. 1—2. PI. VIII. Fig. 10). Most frequently they 

 have a wing-shaped crest on the side turned upwards; sometimes 2 — 3 crests are found, sometimes 

 none at all. Specimens are found, in which almost all the large spines are provided with wings, and 

 other specimens, in which only a few spines or none at all have such crests. The more developed 

 the crest is, the more compressed is the spine, to the very point. Where the crest is wanting, the 

 spines are almost round and rather evenly tapering. There is a somewhat different number '(io~ 16) of 

 projecting longitudinal ridges with rather distinct thorns or dents. In young individuals (and spines) 

 these ridges are more conspicuous, and they are here almost similarly developed, the thorns only a 

 little more conspicuous in one of the ridges. Then the thorns of this ridge increase inordinately in 

 size, and coalesce more and more from the base outward -- and thus the crest is formed (PL XI. 

 Figs. 17, 30, 32). Moreover the whole spine, the ridges (especially the crest), and the intervals are 

 closely covered with delicate, obliquely situated hairs , the points of which are directed upward or 

 outward (on the thorns). In dried specimens the spines are somewhat shagg>-, and have a whitish tint 

 from the air that is found between the hairs as in the hairy coat of a plant. In old spines this tint 

 is not distinctly seen, but in }-oung spines it may be very beautiful. In transverse sections of the 

 spines (PI. XI. Fig. 33) these hairs are seeu to form a thick, complicated network on the outside of the 

 outer layer of the spines. — The large spines are almost always turned directly to the side, so that 

 the animal gets a peculiar flat appearance recalling a wheel (PI. VI. Figs. 1—2). The spines round the 

 mouth are flat, and have most frequently distinct, sharp dents in the edge. 



The secondary spines are exceedingly numerous, and give the animal an almost shaggy appear- 

 ance. Round the radioles a single circle of larger flat spines, of a length of 21/2— 3™'", of the common 

 form is found. In the primary series in the ambulacral areas the spines are somewhat narrower and 

 only about half the length of those round the radioles, scarcely 2""", the other small spines are still 

 much smaller, ca. "2—1™"'. They are not distinctly compressed, and are not strongly pressed against 

 the test, as is otherwise generall_\- the case in the Cidarids. The spines round the radioles and those 

 of the outer series of the ambulacral areas are often a little bent at the point and hollowed on the 

 upper surface (PI. VIII. Fig. 19), which is especialh' the case with the ambulacral spines nearest to the 

 peristome. The spines of the peristome are generally somewhat widened at the point, and liave, as it 

 were, an indication of bisection, a thinner stripe being found downward from the middle of the point 

 (PI. VIII. Fig. 20). There is no iampulla at the base of the spines, at most a slight indication of 



such a one. 



The pedicellariæ : The large globiferous pedicellariæ (PI. VIII. Figs. 11, 16, 29) recall very much 

 those of D. papillata, but by a closer examination they .show no slight difference. There is no 



