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 REVISION OF THE CASSIDULOID ECHINOIDS 



By PORTER M. KIER 



Associate Curator, Division of Invertebrate Paleontology 



and Paleobotany, United States National Museum 



Smithsonian Institution 



(With 44 Plates) 



INTRODUCTION 



During preparation of the chapter on the Cassiduloida for the 

 "Treatise on Invertebrate Paleontology," it became obvious that this 

 group could not be properly understood without considerable research. 

 Morten sen (1948) made a great contribution to knowledge of the 

 cassiduloids, but unfortunately he saw few of the fossil species and 

 was misled by the many inaccurate descriptions and illustrations by 

 previous authors. Only by reexamining the primary types or topotype 

 specimens of the type species, could the systematic outline of the 

 cassiduloids be determined. This task has taken nearly five years, 

 requiring two trips to European museums and extensive borrowing of 

 specimens. Specimens of the type species of nearly all the genera 

 have been studied, including the 71 genera that have been considered 

 as synonyms. The results agree with the findings of Durham (i955» 

 p. 74), that although the illustrations by previous workers appear to 

 be carefully drawn, many are very inaccurate. Furthermore, most 

 authors have not included drawings of the phyllodes, a feature which 

 has proved to be of the utmost importance to the classification of this 

 group. 



The order Cassiduloida, as restricted herein, includes all those 

 "irregular" echinoids having petals, phyllodes, and bourrelets (the 

 floscelle). These structures are illustrated in the included figure of 

 a typical cassiduloid (text fig. i). The phyllodes are formed by the 

 crowding of pores in the ambulacra near the mouth (peristome). The 

 bourrelets are caused by a swelling of the interambulacral plates at 

 the peristome. There are 67 genera and approximately 800 species. 



SMITHSONIAN MISCELLANEOUS COLLECTIONS, VOL. 144, NO. 3 



