BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 

 Vol. 7, pp. 135-170 January io, 1896 



STUDIES OF MELONITES MULTIPORUS-^ i 



BY ROBERT TRA^Y JACKSON AND THOMAS AUGUSTUS JAGGAR, JR 



{Read before the Society August 27, 1895) 

 CONTENTS. 



Page 



Introductory , 135 



Description of spines 136 



Arrangement and development of the ambulacral and interambulacral plates. 138 



Structure and development of the ambulacrum , 140 



Structure and development of the interambulacrum 142 



Variations in the interambulacrum . . : 151 



Imbrication of plates 154 



Genital and ocular plates and discussion of orientation 155 



Tabulations of plate arrangement in the interambulacral and ambulacral areas . 156 



Remarks on the tables of plate arrangement 157 



Tables of plate arrangement 165 



Introductory. 



The remarks in this prefatory statement vrill serve as an introduction 

 for the present paper on Melonites muUiporus under joint authorship, and 

 also for the succeeding paper, " Studies of Palseechinoidea," by myself. 



Deep obligations are due to Mr Alexander Agassiz for the opportunity 

 of studying the rich collections of Paleozoic echinoderms in the collections 

 of the Museum of Comparative Zoology at Cambridge. Besides an ex- 

 tensive series of Melonites muUiporus, this museum possesses a number of 

 generic and specific types and many rare species, as described in the 

 following pages. 



For the opportunity of using material, obligations are also due 'to 

 Professor R. P. Whitfield, of the American Museum of Natural History 

 in New York ; Professor C. E. Beech er, of Yale University Museum ; 

 Mr C. Schuchert, of the United States National Museum ; Professor A. 

 Hyatt, of the Boston Society of Natural History ; Professor William B. 



* Plates and descriptions of the same, also list of references quoted, will be found at the end of 

 the succeeding paper : Studies of Palseechinoidea. References are indicated by a figure in paren- 

 thesis after names of authors cited. 



XIX— Bull. Geol. Soc. Am., Vol. 7, 1895. (135) 



