484 HOLOPNEUSTES POROSISSIMUS. 



in the poriferous zone parallel with the inner vertical row of pores ; others 

 smaller, irregularly scattered, where the tubercles form irregular horizontal 

 rows of from two to three tubercles for each plate. Towards the median 

 space in both areas the plates cany small distant secondaries arranged in 

 continuation of larger horizontal rows in the interambulacra, and irregularly 

 placed in the ambulacra. In the interambulacra] space there is for each 

 plate a larger primary, forming a distinct vertical row, and from one to six 

 smaller tubercles on each side of the median interambulacral line forming 

 horizontal rows and very indistinct vertical rows. The tubercles between 

 the principal primary vertical row and the poriferous zone are not as closely 

 packed as in II. porosissimus. No bare median ambulacra] or interambu- 

 lacra] spaces. The abactinal system is comparatively small, not prominent ; 

 anal system small. Madreporic genital somewhat larger than the other 

 genitals. Ocular plates as in H. porosissimus, disconnected from the anal 

 system, carrying tew secondaries, as well as on the anal edge of the genital 

 plates. 



Color of test, denuded, yellowish-orange or reddish-orange, with the porif- 

 erous zone of a darker tint. 



Holopneustes porosissimus 



! Cidaris granulata (Agass.). 1841. Mon. Scut. 



I Holopneustes porosissimus Ac... 1846, C. R. Ann. Sc. Nat., VI. 



PL Vlir.f. o-io. 



Outline of test globular, test moderately stout. Poriferous zone broader 

 than the median ambulacra] space. Pores forming an outer very regular 

 vertical row, an inner row somewhat undulating, while the remaining broad 

 space is filled by apparently irregularly arranged pores, due to the great lat- 

 eral spreading of the three original narrow plates of the poriferous zone in 

 such a manner that the three pores belonging together form parallel rows, 

 one shorter than the other either inwardly or outwardly, giving to the 

 median space of the poriferous zone the aspect of being filled by irregular 

 oblique lines of pairs of pores, between the inner and outer more regular 



