COELOPLEUHUS FLORIDANUS. 9 



came to the conclusion that Coelopleurus was closely allied to Arbacia, and 

 belonged to the same family, — a view also held by Liitken, from an inspec- 

 tion of Michelin's figures. 



The details which I am able to give regarding Coelopleurus floridanus will, 

 I think, leave no doubt of the correctness of the generic identification of 

 Coelopleurus floridanus and Keraiaphorus Maillardi, and of their systematic 

 position among Arbaciadae. Fragments of the test, and a large number of 

 pieces of larger spines show that the West India species must attain fully the 

 size of the Bourbon species. 



In the young specimens figured (PI. I. f. 6, ~), which are magnified four 

 diameters, the actinostome is large, having already the peculiarly shaped 

 lips of the actinal cuts of all Arbaciadae ; though, as in the young of Arba- 

 cia, the cuts are as yet but mere indentations, and remain so in this genus ; 

 there are two or three deep ambulacral pits between the ambitus and the 

 actinostome. In these young specimens the ambulacral primaries are the 

 only ones extending beyond the ambitus ; the narrow poriferous zone forms 

 continuous arcs round the base of the primaries. In the interambulacral 

 space the primaries extend from the actinostome, slightly beyond the am- 

 bitus, to the bottom of the peculiar, broad, bare, median interambulacral 

 space, which shows as yet only rudiments (minute miliaries) of the marked 

 angular ornamentation of the median part of the interambulacral plates of 

 the larger specimens. 



The ambulacral zones are broader than the interambulacral ones, and are 

 separated from the latter by a narrow vertical row of closely packed second- 

 ary tubercles. Anal edge of genital ring raised ; each genital plate carries 

 in the centre near the anal edge a prominent secondary tubercle, of the same 

 size as those of the vertical row, separating the poriferous zone from the 

 interambulacral spaces, surrounded by a pavement of flat miliaries. The 

 ocular plates carry similar single tubercles on the outer extremity. Anal 

 system elliptical ; madreporic genital slightly raised, but not larger than the 

 others. 



The largest complete specimen dredged by the Hassler is figured, with all 

 its spines of natural size, on PI. I. f. 5. The long curved spines are fig. .i. 

 carried on the primary ambulacral tubercles ; some of them equal three 

 times the diameter of the test. The spines of the interambulacral area, 

 adjoining the poriferous zones, are either rudimentary, attached to the 

 tubercles, or else pointed, with serrate edges (Fig. ::;), as they approach 



