REPORT ON THE ECHINOIDEA. 33 



most south-eastern extremity of the Pacific Ocean we have the fullest possible proof, but 

 that it extended to the west of the Azores we know not, and we must seek other modes 

 of connection, perhaps across the short space between South America and Cape Verde 

 Islands, certainly not by the North Atlantic, but perhaps by the North South Atlantic. 

 The isolation of the West Indian corals, polyps, and echuioderms dates from the time of 

 the shutting ofi" of the Isthmus of Panama, and probably by areas of elevation synckro- 

 nous with the rise of the West Indies. These areas of elevation certainly extended far 

 to the south on the west coast of South America, where we can trace them in the suc- 

 cession of the great inland basins forming the great desert of the narrow rainless belt of 

 the coast, the old sea-bottom now flanked by nitrate beds up to a height of 3000 feet ; 

 where we also find species of corals identical with those now living, or similar at least to 

 those of the West Indies. 



DESCRIPTION OF THE SPECIES. 



DESMOSTICHA. 

 Sub-order Desmosticha, Haeckel, Entwickel. Gesch., 1866 (emend.). 



ClDARlDJE. 

 Family, Cidahid^ MiilL, Bau d. Echinod., 1854 (emend.). 



GoNIOCIDARIDjE. 

 Sub-family Goniocidarida, Hffickel, EntwickeL GescL, 1866. 



Cidaris. 

 Cidaris, Klein, Nat. Disp. Echin., 1734. 



Many attempts have been made to refer some of the recent sul^-genera of Cidaris 

 to genera composed thus far of fossd species only. With the exception of the species of the 

 genus Cidaris proper, these attempts must be considered faulty, from the usually im- 

 perfect state of preservation in fossils of some of the most important characters by which 

 the recent sub-genera have been distinguished. Such important guides as the nature of 

 the pedicellariee and the structure of the abactinal system are wholly wanting for com- 

 parison, and the difiiculty of deciding on the relationship from the test and radioles 

 alone, is too well-kno'^vai to require further comment. In fact, setting aside Di2:>locidaris, 

 Porocidaris, and Goniocidaris, which are separated from Cidaris proper by characters 

 apparently more prominent and permanent than those upon which the other genera 

 among the fossil or recent species are based, we must consider Dorocidams and Phylla- 

 canthus as mere sub-genera of Cidaris, convenient subdivisions round which a large 

 number of recent and fossil species can be arranged. Dorocidaris would include all 



(ZOOL. CHALL. EXP. — PART IX. — 1881.) I 5 



