CLASS I 



ECHINOIDEA 



311 



characters seen in the adults of the preceding series, or lower members of its 

 own series. 



Geological Range of the Echini 



[To Dr. Robert Tracy Jackson, of the Boston Society of Natural History, acknowledgments 

 are due for having revised the preceding chapter on Echinoidea. A number of new illustra- 

 tions have been reproduced from this author's recently published monograph on the Phylogeny 

 of the Echini. — Editou.] 



