,Q ECHINOIDEA. II. 



pores being placed in these depressions. The innermost ones are directed alniost straight towards the 

 border of the peristome, farther out they beconie parallel to the ambitus; the same feature is seen in 

 the arrangement of the pores as seen from the ontside of the test. (PI. XII. Fig. 27). 



Among the tubercles are seen some mostl)- ronnded, sometimes irregular, glassy protuberances 

 about as large as the priniar\- tubercles; the\- are onh- elevations from the test, not carrj-ing spines or 

 pedicellariæ. They are speciallx numerous on the actinal side (PI. XII. Fig. 26), and when seen under 

 the microscope are ver\- conspicuous among the white tubercles on account of their smooth, shining 

 surface. On the abactinal side thev are less numerous; such a protuberance is generalh' situated be- 

 tween the two pores of each pair of the petals, elongated in shape and with a distinct longitudinal 

 fiurow in the middle. (PI. XII. F'ig. 22.) 



The spines are short, niaking a dense clothing. The primar\- one.s, about 0-5— 07™'" long, are 

 .slightly tapering, densely serrate, except at the base (PI. XII. Fig. 19); those around the peristome are 

 curved. Generally they are a little thicker in the middle, as seen in the figure cited; sometimes they 

 are distinctly widened in the outer part. The point is generally worn off. As pointed out by Agassiz 

 those on the actinal side are somewhat longer than the abactinal ones. The miliar\- spines (PI. XII. 

 Fig. 9, 18) are only about half the .size of the primar>- ones, a little widened in the point, which forms 

 a sort of crown, the -endcrown of de Meijere, to whom belongs the merit of having shown the 

 great systematic importance of the structure of the spines, especialh" the miliaries, in the Clypeastroi- 

 dra. (<Siboga -Echinoidea. p. 113). The longitudinal ribs are .slighth- widened above with the edge 

 fineh- serrate, sometimes almost smooth. The small radial piates in the crown are simple or with a 

 few (2, sometimes 3 or 4) dentations. It is worth noticing that, when the living animals are put in 

 alcohol, the spines turn intensel\- green; this holds good also for several other Chpeastrids, if not 

 for all of them. • 



The pedicellariæ are represented by three kinds, viz. ophicephalous, tridentate and triph\llous. 

 The ophicephalous pedicellariæ (PI. XII. Figs. 4, 6) are small and rather simple in structure: the blade is 

 narrow, elongated, widening a little in the onter part; the edge is somewhat densely serrate along 

 the whole length. There is no distinct basal part; the articular surface is very strongly developed, 

 the three valves articulating so closeh' together that it is almost impossible to separate them with- 

 out breaking (in EcJi. graiidiporns the valves separate easily). In one of the \alves the are is ver\- 

 large; another has the are prolonged into a long thornlike proce.s.s, which goes through the hole in 

 the large are; its point is more or less bent. The third vahe has the are \ery slighth' developed, with 

 no proccss. (Comp. PI. XII. Figs. 8, 11, 12 of Ec/i. grandiporits]. This structure is well seen in the figure 

 given by Cuénot (op. cit. — he wrongly names it a tridactyle pedicellaria); de INIeijere also gives 

 a description of it (op. cit. p. 108). The head articulates directl\ with tlie upper end of the .stalk, 

 the large are resting on the cup-shaped upper end of the stalk, attached b\' some muscular fibres to 

 the bottom of the cup, as shown in Cuénot' s figure, The stalk is comparativeh very robu.st, almost 

 hourglass-shaped, in the middle part it consists of compact calcareous substance, at both ends it is 

 of the common, looser structure. These pedicellariæ are especialh numerous on the actinal side, 

 behiud the anal area. — The triph\-llous pedicellariæ (PI. XII. Fig. 20) are very small, the head not 

 more than ca. 0-04"""; the stalk is like that of the ophicephalous pedicellariæ, onh much more slender 



