PREFACE. 



Although published more than half-a-century ago, the " Synopsis des Échinides 

 Fossiles," by Pierre Jean Edouard Desor, is a work still in constant use by every 

 serious worker on the Echinoidea. I say every worker, and not only every 

 palaeontologist, for two reasons. First, the book, though professedly deaHng 

 with fossils, does actually contain several purely récent gênera and species. 

 Secondly, niany of the gênera, though included on account of their fossil 

 représentatives, are not entirely extinct, so that the student of the récent species 

 is bound to consider their fossil allies and to take into considération the names 

 given to them. 



Unfortunately référence to this work bas ahvays been rendered difficult by 

 the lack of an index, a want that is felt more and more as time goes on, and 

 as the various gênera are sub-divided, and the species, for that or other reasons, 

 appear under différent generic names from those in the Synopsis. The présent 

 Index, therefore, bas been prepared on the plan followed in the well-known 

 " Index Animalium " of Mr. C. Davies Sherborn. It consists, that is to say, of 

 two parts : in the first the species are arranged alphabetically under their trivial 

 names ; in the second the generic names are indexed, and each such name is 

 followed by the number of the page on whicb its diagnosis occurs, and then by 

 every trivial name that is anywhere associated with it in the Synopsis. The 

 names of gênera are also placed in their alphabetical position in Part I. 



Certain détails of the indexing require explanation. In drawing up the 

 alphabetical order of Part I., no attention has been paid to the masculine, 

 féminine, or neuter endings of one and the same adjective ( — ns, — a, — //;//, 

 and ■ — is, — e), but the séquence under that trivial name is determined by the 

 alphabetic order of the generic names with which it is associated. This is the 

 more necessary because Desor was not ahvays either consistent or correct in bis 

 use of gender. 



When names are spelled incorrectly or inconsistently by Desor, they are 

 indexed as he spelled them, but a cross-reference to the correct spelling is given 

 whenever it seems désirable. The same course has been followed with such 

 variants as Cidaris and Cidarites, which clearly were not intended to represent 

 distinct gênera. 



In Part I. a référence is given to every page on which a name occurs, as 

 well as to the plates. The only exceptions are the pages of the Avertissement 

 (vii.-xlvi.), of the Tableau de la Distribution (xlvii.-lxviii.), which in itself 

 constitutes an index of a différent kind, and of the Tableau des Synonymes 

 (455-483), which is yet anothcr kind of index. Certain names or associations 

 of names are, however, only to be found in thèse Tableaux, and bave, therefore, 

 been indexed. The indexing of the Plates is an important feature, since 



