2 PBOF. P. M. DTJNCATS S EEVISION OF THE 



1883, Expeditious, by this author, contain nearly the whole of 

 tlie systematic and mucli of the morphological knowledge of the 

 recent fauna. The work of Desor, and those of A. Agassiz, the 

 one on the fossil, and the others mainly on the recent genera 

 and species, are invaluable and have formed the basis of all 

 subsequent research. But no book has appeared which has been 

 written by any naturalist who has personally laboured in the 

 classification and morphology of the Class, which has treated of 

 both the fossil and the recent genera. Palaeontologists have 

 published great numbers of genera and species since the days of 

 Desor, and have not invariably paid attention to the progress of 

 their fellow workers who have described recent forms. And, on 

 the other hand, much that was written a few years since by some 

 naturalists, dealing with recent forms, would not have seen the 

 light had careful descriptions of fossil genera, such, for instance, 

 as have been published by Cotteau, de Loriol, and Sven Lnven, 

 been available in a standard work of reference. The results of this 

 division of labour and of the independent researches of Palaeon- 

 tologists and Zoologists have been the adoption of too many 

 genera and the production of much confusion in the nomea- 

 clature ; and the recognition of genera and species, both fossil 

 and recent, has been rendered difiB.cult by the publication of their 

 diagnoses in the Journals of learned Societies, and in the works 

 of Greological Surveys of nearly every civilized country. 



The progress of the morphology of the recent Echinoidea has 

 been great, and it chiefly dates from the time of J. Muller (1854) 

 and the subsequent publication of S. Loven's ' Etudes sur les 

 Echinoi'dees ' in 1874 ; it was maintained by the author of the 

 ' Eevision of the Echini,' and much valuable new matter is to 

 be found in the ' Challenger ' and ' Blake ' Reports. Loven's 

 wonderful work on Pourtalesia and his later contributions, 

 together with the results of the work of Sir Wy. Thomson, and 

 of Messrs. Norman, Stewart, Ludwig, PI. Carpenter, Sladen, 

 Hamann, Saiasin, and Bell, and of some publications in the 

 Journals of the Linnean and Geological Societies of London, 

 have rendered some modifications in the terminology and of the 

 taxononiic value of certain structures absolutely necessary. 

 It is the belief of all practical Echinologists that a work 

 which would collect the generic descriptions of both the fossil 

 and recent faunas, and which would revise and eliminate 

 when necessary, by the light of modern morphology, is very 



