8 COELOPLEURUS FLORIDANUS. 



ligera, both of which, according to the comparison of original specimens with 

 others of undoubted locality, are found on the west coast of South America. 



Coelopleurus floridanus 



! Coelopteurw floridanus A. Ac, 19 72, Rev. Ech., Pt. I. p. 102. 



PlI.f.B-7. 



Troschel has limiterl the family of Echinocidaridae to the old genus 

 Echinocidaris, and does not include in it either Podocidaris or Coelopleurus, 

 which I believe belong to the family of Arbaciadae. As for Podocidaris 

 the merest inspection of the figures (on PI. IV. f. 8-15, Rev. Ech.) and 

 comparison with the figures of young Arbacia (PI. V., Rev. Ech.) cannot 

 fail to show such a close homology that at first sight Podocidaris would 

 most naturally be considered the young of some species of Arbacia. If 

 we add to this the structure of the spines, of the poriferous zone, of the 

 tentacles, of the pedicellarise, of the abactinal system, and of the actinostome, 

 all of which are strikingly similar to the structure of corresponding parte of 

 Arbacia, I think I am justified in placing Podocidaris among the Arbaciadae. 



Where Troschel conceived the idea that I had associated Parasalenia and 

 Trigonocidaris with tin' Arbaciadae I am at a loss to know. As regards 

 Coelopleurus, the additional details here given of Coelopleurus floridanus 

 will. I think, convince Professor Troschel thai my association of the spines 

 figured on PI. II . f. /;, /.; (Rev. Ech.) with Keraiaphorus Maillardi was 

 correct. Their generic identity I should never have dared to suggest or 

 even to defend, from fragments of single spines, for any other genus of 

 Echini ; hut in this case the spines are so unlike (the long abactinal spines) 

 anything else known among Echini, either living or fossil, that had Profes- 

 sor Troschel ever seen the spines of the Bourbon specimen, he would not 



have hesitated to identify the genera There were in Cambridge a number 

 ..f spines of Keraiaphorus, given to me by Professor Bayle ; my identi- 

 fication h:i- made after careful comparison of the external appearance and 



structure of the spines. 



The figures of Coelopleurus (Keraiaphorus Maillardi i given by Michelin 

 seem to have escaped Troschel, for lie certainly would not have doubted 

 the position of the genus among Arbaciadae, as he has done : and after 

 comparing them with Coelopleurus, he could not fail to sec their identity. 

 At the time of my rail to the Boole dea Mines I made a most careful com- 

 parison of the test of Keraiaphorus, of Coelopleurus, and of Arbacia, and 



