36 



ECHINOIDEA. I. 





more closely covered with tubercles; there are ca. 15 on the edge of each areole, and outside of these 

 there is a circle of tubercles opposite to the intervals of those of the first circle. Outside of these 

 again several tubercles are found, more or less circularly arranged, so that the whole plate is covered, 

 with the exception of a quite narrow stripe at the median line, — and on the lower part of the test 

 it is also covered by the tubercles. No furrows in the edge of the plates. In the depth of the 

 areoles there seems to be no distinct difference between the two forms. 



The ambulacral area is more peculiar (PI. VI. Fig. 9); the secondary tubercles lie here in the 

 lower edge of the plate, so that they are situated opposite to the intervals between the primary ones 

 (in D. papillata they, as described above, are placed in the middle of the ambulacral plates, opposite 

 to the primary tubercles). The whole form of the ambulacral plates is consequently somewhat dif- 

 ferent from that of D. papillata. Only on the very uppermost and lowermost plates of the area the 

 secondary tubercles are wanting; in the middle part of the area inside the secondary series some 

 tubercles are found still a little smaller (the secondary tubercles are somewhat smaller than the primary 

 ones), placed opposite to the intervals between the secondary tubercles, and consequently opposite to 

 the primary ones, not, however, very regularly. - - The pore area is a little more than half the breadth 

 of the interjacent space, comparatively a little broader than in D, papillata, scarcely, however, of any 

 great importance. 



The spines 1 — i z / 2 time the diameter of the test (in D. papillata ca. 2— 2'/ 2 times); they are 

 evenly tapering, and end bluntly. About 18 longitudinal series of coarse serrations. Between these 

 longitudinal series fine, slightly branched thorns are found, which do not coalesce and form a reticu- 

 lation as in D. papillata (transverse section PI. XI, Fig. 1). The radioles round the mouth are short, 

 blunt, somewhat flat, without any dents in the edge, what they commonly have in D. papillata. As 

 in this latter an ampulla is found at the base of the small spines, especially well developed at those 

 of the apical area. There seems to be no difference of any importance in the form of the small spines 

 of the two species. 



The pedicellarise are of the structure characteristic of the genus Cidaris. The large globiferous 

 pedicellarise (PI. IX. Figs. 9, 22, 24): the mouth is situated quite at the top of the blade which is round 

 and somewhat bent inward; it is surrounded by a limb that is a little bent outward and provided with 

 rather large teeth the number and size of which is rather irregular. The upper end of the mouth has 

 no limb nor any teeth; no end-tooth. The edge of the blade towards the point irregularly dentate. - 

 At the transition between the broad and the narrow part of the stalk a limb is found of freely pro- 

 jecting, short calcareous ridges, prolongations of the rind-layer of the thick part of the stalk (PI. IX. 

 Fig. 12). This limb is most developed on the large globiferous pedicellarise, but may also be rather 

 distinct on the small pedicellarise and the tridentate ones. The whole stalk is far more regularly 

 constructed than in D. papillata : here the outer layer consists of smooth longitudinal ridges with small 

 knob-like swellings, in D. papillata it is an extremely irregular, more or less spinous reticulation. — 

 Size: the head ca. o7 mm , the stalk ca. 2 mm , but especially the latter is rather varying. 



The small globiferous pedicellarise are of a quite different structure (PI. IX. Figs. 8, 11); they 

 have a distinct end-tooth, and the mouth is large and situated a little below the point. The back-side 

 of the blade is almost without the common holes in the lime, only the basal part is perforated as 



