THE MESOZOIC ECHmODERMATA OF THE UNITED 



STATES. 



By William Bullock Clark. 



INTRODUCTION. 



The need of a revision of American systematic paleontology is nowhere 

 more apparent than in the subkingdom of the Echinoderniata. The val- 

 uable contributions of Wachsmuth and Springer upon the Paleozoic 

 Crinoidea have largely covered the field for that division, while as yet 

 nothing exhaustive has been attempted for the Mesozoic and Oenozoic. 

 The value of the Echinodermata in the later horizons may not be so great 

 as in the earlier, yet many important forms of wide geological and geo- 

 graphical range are found in both the Mesozoic and Cenozoic. 



The reports of Morton upon Atlantic Coast species and of Eoemer and 

 Shumard upon Texan types are among the most important publications 

 npon North American Mesozoic Echinodermata, but the articles are in 

 each case difficult of access to the student and the results recorded 

 wholly inadequate for present systematic or stratigraphical require- 

 ments. 



In previous discussions of North American Echinodermata no at- 

 tention has been paid to the South American forms, so that much con- 

 fusion exists as to the true relations of the two faunas. Very little is 

 known of the geographical range of the various species, but that many 

 of the North and South American forms described under different names 

 are identical is beyond doubt. When more exhaustive collections have 

 been made and comparisons instituted, this similarity of echinoderm 

 faunas in the two continents will be made apparent. The present poor 

 descriptions and meager figures afford a very inadequate basis for such 

 a study. 



The identity of American with European species seems doubtful, al- 

 though a few forms i)resent characters that closely ally them. 



In the succeeding pages is presented a complete bibliograi)hy of 

 works on North American Mesozoic Echinodermata, and of certain 

 others that deal with closely related forms. 



In the systematic review that follows, and that constitutes the major 

 portion of the report, descriptions of moderate length are accorded the 



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