452 Forty-fifth Report on the State Museum. 



an epitome or synopsis of that volume, and also including the 

 preceding volumes, so far as related to the brachiopoda, which 

 might bring before the student a clearer appreciation of the 

 generic features of this class of fossils. With this idea in mind 

 arose the conception of treating this subject in the order of 

 geologic time. To one who had worked among the fossils 

 of the older rocks upward through all the formations to the 

 Carboniferous, it was impossible to avoid the conviction that the 

 modification of similar forms in successive geologic periods, and 

 the final disappearance of some of them, either from slow 

 degeneration, or after extravagant manifestations of certain 

 characters, had a significance which had not been fully under- 

 stood or appreciated by writers upon this class of fossils. 



With this conception in mind I began the preparation of what 

 was then intended to be a supplement to Volume IV of the 

 Palaeontology of New York. After waiting for more than 

 twenty years for the means of making the necessary collections 

 and for publication, this supplement has expanded into volume 

 VIII, parts i and ii of the Palaeontology of New York. From 

 the studies carried forward among the brachiopoda in preparing 

 these volumes has come back to the writer more strongly than 

 ever the importance of preparing a synopsis of the genera which 

 may form a useful handbook for advanced students in geologic 

 studies. 



Through the action of an intelligent Legislature and the appre- 

 ciation of a wise Executive, means have been furnished for 

 making this publication. 



The discussions of the genera and their relations are the same 

 as those given in the volumes just named, with corresponding 

 illustrations. 



In order to present the subject to the student, in not too 

 \brupt a manner, it has seemed necessary to precede the generic 

 discussions by some general elementary explanations. 



4 



