BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 



Vol. 7, pp. 171-254, PLS. 2-9 JANUARY 31, 1896 



STUDIES OF PALiEECHINOIDEA 



BY ROBERT TRACY JACKSON 



(^Read before the Society^ August 27, 189S) 



CONTENTS • 



Page 



Studies of the Melonitidse 172 



Introduction 172 



Description of Melonites giganteus, sp. nov 172 



Description of Melonites septenarius, sp. nov. (R. P. Whitfield) 182 



Consideration of Oligoporus and comparison of the same with Melonites 184 



Description of Oligoporus missouriensis, sp. nov 184 



Description of Oligoporus coreyi 186 



Arrangement and development of plates in Oligoporus coreyi 188 



Description of plate arrangement in Oligoporus danse 193 



Consideration of Klioechinus and Falasechinus 200 



Notes on earlier studies 200 



Structure and plate arrangement of Rhoechinus gracilis 201 



Notes on Rhoechinus burlingtonensis 203 



Observations on Falasechinus gigas and Rhoechinus elegans 204 



Studies of the Lepidesthid^e, fam. nov 206 



Relationships and characteristics 206 



Description of Lepidesthes wortheni, sp. nov 207 



Notes on other species of Lepidesthes 209 



Description of Pholidocidaris meeki, sp. nov 210 



Studies of the Archaeocidarid^e 213 



Structure and plate arrangement of Archseocidaris wortheni and other species . 213 



Structure of Lepidocidaris squamosus 220 



Notes on Xenocidaris 222 



Studies of the Lepidocentridae 222 



General characteristics 222 



Structure and plate arrangement of Lepidocentrus 222 



Notes on Perischodomus ; . . . 225 



Structure and development of Lepidechinus 226 



Conclusions 229 



General results and their bearing 229 



A proposed new classification of Paleozoic Echini, with a systematic table 



of the several groups 238 



Basis of the classification 238 



Subclass Palseechinoidea — Order I, Bothriocidaroida 238 



Subclass Euechinoidea 239 



Subclass Palseechinoidea — Order II, Perischoechinoida 239 



XXIV— Bull. Geol. Soc. Am, Vol. 7, 1895. (171) 



