THE DEVELOPMENT OF SOME SILURIAN BRACHIOPODA 



By John M. Clarke and Charles E. Beecher* 



INTRODUCTION 



The fossil faunas of our rock systems rarely furnish material for trac- 

 ing the individual development of any of the contained species. Much 

 will doubtless be done toward ascertaining such development when large 

 collections from suitable localities have been studied with this object in 

 view, and when the number of new species discovered and described each 

 year approaches a minimum. We have a comparatively full and satisfac- 

 tory account of the development of the individual organism in several 

 species of trilobites, as given in the works of Barrande, Walcott, Ford 

 and Matthew; Hyatt, Branco, Mojsisovics and others have demon- 

 strated the developmental characters of many of the fossil cephalopods, 

 and Verworn has elicited similar facts from certain extinct species of 

 ostracoda. Farther than this but little has been attempted, although the 

 field is a most extensive, important, and inviting one. 



As a general rule, the treatment of fossil organisms has rested mainly 



* The order of the names of the authors of this paper is without significance. The work 

 was equally divided and jointly reviewed. 



