KCinXOIDKA. I. 



143 



Agassiz: Revision of Echini, p. 491. -~ \\'y\-. Tlionison: Hchinoidca ot Porcnpinc (395) p. 744. — 

 Hoyle: Rev. List of Brit. Echinoidea (202) p. 414. — Bell: Catalogue of Brit. Echinoderms. p. 154. 



The form of the test rather var\ing, from evenly rounded to slightly conical, on the actinal 

 side evenh- rounded or almost flat (in the conical forms); the edge of the mouth always somewhat 

 bent inward. The peristome rather large. The height of the test a little more than half the diameter; 

 the contour round. 



The ambulacral areas (PI. XVI. Fig. 19) a little more than half as broad as the interambulacral 

 ones, at the edge of the mouth generally a little broader than the latter. The number of ambulacral 

 plates is rather constant, one third as great as that of the interambulacral plates. The boundaries 

 between the primary plates generally somewhat indistinct; the boundary line between the areas not 

 much sinuate. The arcs of pores rather .steep; the pores reach quite to the edge. vSometimes four 



.^U the measures are in millimetres. 



pairs of pores are found in an arc. The primary tubercles are rather large and strong, somewhat 

 smaller than the interambulacral ones, and form a ver\- conspicuous, uninterrupted longitudinal series, 

 a primary tubercle being found on all the plates. They are placed very close together, the edges of 

 their scrobicular areas join through almost the whole area onl\- the \-er\- uppermost ones are sepa- 

 rated. This fact of the tubercles being placed so close together gives to the test a very charac- 

 teristic appearance. The secondary tubercles ma> form a short longitudinal series on the actinal side 

 in.side of the primary series, but this feature is not a constant one. On the abactinal side there are 

 only few secondary tubercles; commonly there is one small tubercle between the pores and the prim- 

 ary tubercle. Miliary tubercles numerous and rather strong; together with the secondary ones they 

 give the whole test a very rough and uneven appearance. (In the figures the miliary tubercles have 

 been omitted.) 



The interambulacral areas (PI. XV. Fig. 4). Also here the priniar\' tubercles form a very close 

 series, the scrobicular areas, however, do not join above the ambitus. The secondary tubercles are 

 very numerous on the actinal side; they are considerably smaller than the priinar\- ones, and form 

 no distinct longitudinal series neither iiLside nor outside of the primary ones. 



The apical plates carr>- rather manv tubercles (PI. XVI. Fig. 3). The periproct is generalh- very 

 .small (in the figured one it was larger than is commonlv the fact), covered by numerous, irregular 



') The specimen figured on PI. I. Fig. 2. 

 -) The specimen figured on PI. I. Fig. 3. 



