10 COELOPLEURUS FLORIDx\NUS. 



the ambitus. On the actinal side the spines of both areas are identical ; 

 they consist of a finely serrate base, above the milled ring, extending half 

 the length of the spine ; the upper part is flat, spathiform, with sharp 

 edges ; the flat portion of the spine having the amorphous, finely granular 

 {Figs. 4, 5, g) structure of the large spines already described in the Revision 



Fig. 4. Fig. 5. Fig. 6. Fig. 7. 



of the Echini. As the spines grow older the serrated collar loses its promi- 

 nence (.F/ff. 7), and the large ambulacral spines of the abactinal surfiice appear 

 Tmiformly granular, with a delicate suture somewhat above the milled ring. 

 The S'Shaped curves, so prominent on the abactinal interambulacral spaces 

 of the Bourbon species, are quite apparent in our largest specimens ; the 

 miliaries forming independent patches or triangular figures, extending al- 

 ternately from the median line of the plates towards the poriferous zone. 

 The miliaries carry pedicellaria) on long, stout stems, like those of Podo- 

 cidaris, with a comparatively small head. The ambulacral suckers are pointed 

 towards the abactinal pole, as in all Arbaciadae, and have prominent, well- 

 developed suckers on the actinal side. The actinal membrane is bare, with 

 the exception of ten large buccal plates, which carry clusters of small jDcdi- 

 cellariae. The teeth do not differ from the teeth of the Bourbon species and 

 of the Arbaciadae. 



The anal and ocular plates carry small pedicellaria3 and minute rudimentr 

 ary spines. The long collar of the base of the primary spines reminds us of 

 a similar structure in Porocidaris, figured by Thomson * in his Depths of the 

 Sea. The outer granular part of the spines of this genus is formed subse- 

 quently as a tip to the basal portion, without the usual cellular sheath which 

 forms the longitudinal serrations of Echini spines. This gives us an explana- 

 tion of the apparently anomalous structure of the base of the older spines of 

 these two genera, which appear as if they had been broken off" and soldered 

 again. This granular addition is the homologue of a similar tip, which is found 

 in all Arbaciadae, and has been particularly well described by Desraoulins. 

 It remains always as a flat, spathiform appendage in the shorter spines of 



* Thomson, W,, The Dopths of t.lu> .Sea. 1873, p. 102,/ 11. 



