14 THE MESOZOIC ECHINODERMATA OF UNITED STATES. [bull. 97. 



different species. It has been deemed sufficient to present simply those 

 characteristics that are necessary for an accurate determination of the 

 forms, omitting many of the minute though interesting details of 

 structure. A table is given showing the geological range of the dif- 

 ferent American Mesozoic species. In conclusion an index to the various 

 terms employed by those who have written on the Mesozoic Echiuoder- 

 mata of the United States is presented. 



An attempt has been made to very fully illustrate all the species. 

 Many of the details of structure, not recorded in the descriptive portions 

 of the report, are shown on the various figures. 



