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GENERA OF TERTIARY AND RECENT 

 RHYNCHONELLOID BRACHIOPODS 



By G. ARTHUR COOPER 



Head Curator, Department of Geology 



United States National Museum 



Smithsonian Institution 



(With 22 Plates) 

 INTRODUCTION 



For several years the writer has been studying the few brachiopods 

 known from the Tertiary formations in the eastern United States. 

 Most of the species are terebratuloids but a few rhynchonelloids ap- 

 pear in the collection. The Palmer collection of Cretaceous and Terti- 

 ary brachiopods from Cuba was also made available. This collection, 

 too, contains a few rhynchonelloids. This group of brachiopods seems 

 to be unusual in Tertiary deposits and the same is true of the rhyncho- 

 nelloids of modern seas. In the study of the Tertiary forms it proved 

 necessary to compare them with modern representatives. In making 

 these comparisons it became evident that modern rhynchonelloids 

 have been well described in only a few instances and very few of them 

 have ever been adequately illustrated. Inasmuch as the collection of 

 Recent brachiopods in the National Museum contains a good repre- 

 sentation of modern rhynchonelloids, the opportunity presented itself 

 to correct the deficiencies outlined above. 



In addition to the American Tertiary rhynchonelloids, some species 

 from outside North America are also included. The National collec- 

 tions do not contain many representatives from foreign Tertiary de- 

 posits but some good specimens are available from the Mediterranean 

 region and elsewhere. These made possible the figuring and descrip- 

 tion of some new or little-known genera. 



Although this monograph adds considerably to our knowledge of 

 Recent and Tertiary genera of rhynchonelloids it does not include all 

 the known species or all the possible genera. A number of species are 

 known from European deposits but the interior details have never been 



SMITHSONIAN MISCELLANEOUS COLLECTIONS, VOL. 139, NO. 5 



