THE 



DEVELOPMENT OF GLYPHIOCERAS AND THE 



PHYLOGENY OF THE GLYPHIOCERATID^. 



BY JAMES PERRIN SMITH. 



CONTENTS. 



Page. 

 Plates XIII-XV. 



Introduction 105 



Classification of Goniatites 107 



Glyphioceratid^ loS 



Glvphioceras ... no 



Glyphioceras incisum Hyatt in 



Larval Stages 114 



Phylembryomc 114 



Ananepionic 1 16 



Metanepionic 116 



Paranepionic 117 



Adolescent Stages 117 



Neanic 117 



s Adult Stage 1 20 



Table of Stages of Growth 121 



Summary of Results 121 



Explanation of the Figures 124, 126, 128 



Introduction. 



All modern classification is intended to be genetic, but in 

 reality is usually not so, being based not on ontogenetic 

 study, but rather on a comparison of supposed genetic series 

 of adults. Much that has passed for demonstration has 

 been in fact only conjecture. The only safe way is com- 

 parative study of ontogeny with series of adults — real phy- 

 logeny. This method of work is difficult to pursue with 

 living forms, and still more so with fossils, although much 

 that is good and reliable has been done with both. 



The fossils that best lend themselves for this sort of work 

 are the Amnionoidea, a group of cephalopods that lived from 

 the beginning of the Devonian to the end of the Cretaceous. 

 Being wholly extinct, the group is classified entirely by ex- 

 ternal markings, such as are capable of being preserved in 



[ 105 ] October 12, 1897. 



