STEPHANOCIDARIS. 393 



greenish, tipped with a darker shade of the same color. The primary spines 

 are of brownish tinge, with three to four greenish or yellowish-green rings ; 

 the granulation is coarse, arranged in longitudinal rows, frequently forming 

 lamellae at the base of the swellings along the shaft of the spines. 



The abactinal system is but sparingly covered by papilla? ; the genital 

 openings are small ; the ocular plates triangular ; the anal system pentagonal ; 

 the genital plates, with one exception, where they are separated by ocular 

 anal plates, are connected laterally. 



Society Islands ; Australia ; East India Islands. 



STEPHANOCIDARIS. 



Stephanocidaris A. Ac, 1863, Bull. M. C. Z., I. 



The peculiar structure of the abactinal system in this genus is thus far 

 the only exception to the remarkable uniformity of structure of the solid 

 abactinal system of all Cidaridae, in which the abactinal plates are generally 

 solid, stout, immovable, and more or less covered with granules ; in Gonio- 

 cidaris we find in one of the species the outer edge of these plates free from 

 tubercles, smooth. In this genus the whole abactinal system is thin, mov- 

 able, resembling, in fact, far more the flexible anal system of Echinidae 

 proper than the massive abactinal system of Cidaridae. The test is also 

 exceedingly thin, but the remaining structural features of the test, spines, 

 and buccal membrane do not differ essentially from those of the other 

 Cidaridae. The number of primary tubercles is large ; the poriferous zone 

 as in Phyllacanthus. 



Stephanocidaris bispinosa 



! Cidarhes bispinosa Lam., 1816, An. s. Vert. 



! Stephanocidaris bispinosa Ac, 1872, Rev. Ech., Ft. I. 



Pl.r.f.43; PLF.f.s. 



Test thin, and further distinguished from all other Cidaridae by the struc- 

 ture of the abactinal system, made up of thin flexible plates. Abactinal 

 system much larger than the actinal. Genital plates pentagonal, elongate ; 

 genital openings small, sometimes two for each plate. Ocular plates 

 large, trapezoidal, completely separating the genital plates. Whole abac- 

 tinal system moderately closely packed with miliaries. 



Median ambulacral space broad, with five irregular vertical rows of mili- 



