PHYLLACANTHUS ANNULIFERA. 387 



(CIDARIS.) Phyllacanthus. 



Phyllacanthus Brandt, 1835, Prod. Dese. An. 



Brandt was the first to separate Cidaris into two sections, distinguished, 

 it is true, by the rather meagre character of straight and flexuous poriferous 

 zones. Yet the species he mentions as belonging to his two sections corre- 

 spond so well to the modifications subsequently introduced by Desor, that 

 we cannot help retaining his subdivision. Desor has separated as Rhabdo- 

 cidaris (crenulate tubercles, fossil) and Leiocidaris (no crenulation, recent), 

 the fossil and recent species, — a character which he has not adopted as 

 of generic value in Cidaris proper ; and there appears to be, at present at 

 least, no reason for assuming this feature to have any great value. 



Test swollen, comparatively thinner, and with a larger number of coro- 

 nal plates than in Cidaris. Ambulacra almost straight or very slightly 

 undulating. The poriferous zone is broad, the pores of a pair connected by 

 a slight horizontal furrow. The primary spines vary greatly in shape, — 

 cylindrical, triangular, flattened, club-shaped, elongate, fluted; granulation 

 longitudinal, often forming highly developed lamelloe or simply close longi- 

 tudinal stria?, or rows of secondary spines. Tubercles perforate, mammary 

 boss smaller than in Cidaris ; scrobicular circle large, with very prominent 

 granules ; areola deeply sunken. 



Phyllacanthus annulifera 



! Cidariles auuulifera Lam., 1816, An. s. V. 



! Phyllacanthus annulifera A. Ag., 1872, Rev. Eeh., Pt. I. p. 150. 



PI T.f. 21-26*. 



Genital plates separated from the large triangular ocular plates by bare 

 sutures. Genital openings large, near outer edge of plates. Miliaries cov- 

 ering the abactinal system distant and confined to central part in ocular 

 plates. Anal plates of nearly uniform size, each plate carrying but two or 

 three miliaries. Anal plates encroaching between the genital plates. Me- 

 dian ambulacral space narrow, with two vertical rows of miliaries between 

 the two external rows of secondary tubercles. Median interambulacral 

 space narrow, with but few small miliaries in addition to secondaries ; median 

 sutural line well marked. Scrobicular circle very distinct, formed by a 

 double row of secondary tubercles. 



