PREFACE. xiii 



toward the structure and classification of the genera were made by Zittel, 

 ffinLERT and Waagen, and communications of no little importance relating to 

 structural characters of genera and species, appeared from all quarters of the 

 scientific world. 



The multiplicit}' of these communications is indicated in part hy the biblio- 

 graphic tables presented in this volume ; they also show the wide-spread inter- 

 est in the Brachiopoda, not only among students of biology, in their structure, 

 morphology and taxonomy, but among geologists, in their value as stratigraph- 

 ical indices. American students have heretofore labored under a disadvantage 

 in the irregular diffusion of the literature of the Brachiopoda. Much of the 

 European literature is inaccessible except to those working in the vicinity of 

 extensive libraries; the American literature is so scattered through scientific 

 periodicals, proceedings of various societies, etc., as to be frequently inaccessible. 

 Furthermore, while the more general treatises of Zittel and (Ehlert may be 

 in the hands of many, the gi'eatest of all works upon the subject, that of Thomas 

 Davidson, is beyond the reach of but a very few. 



With this volume, therefore, is presented, especially to American students, the 

 first part of "An Introduction to the Study of the Genera of the Palaeozoic 

 Brachiopoda," a work not conceived upon the plan of any of its predecessors, 

 but designed to set before the student the present condition of our knowledge 

 of these genera, with such discussions and illustration as will serve most 

 clearly to indicate what progress has been made in our knowledge of these 

 organisms and in what directions much still remains to be done. 



In the preparation of this work every effort has been made to bring under 

 close and careful scrutiny all obtainable material representing the Brachiopoda. 

 The collections of no single institution or individual could furnish the speci- 

 mens requisite for this undertaking, and recourse has been had to all sources of 

 material within reach. The collections of private individuals as well as of 

 public institutions have been placed at the disposal of the work, and but for 

 such aid it could not have been presented in a creditable form. 



My acknowledgments are especially due to Sir William Dawson, Principal 

 of McGill University, Montreal, Canada, for specimens and valuable informa- 



