6 CONTENTS. 



Chapter IV. Morphology of the brachia, hy Charles E. Beecher — Continued. 



Classification of brachial structures — Continued. Pago. 



Ptycholophus stage 109 



Zugolophus and plectolophus stages 109 



Spirolophus stage 110 



References 112 



Chapter ^^ Classification of the IJrachiopoda 113 



Historical 113 



Principles of classification 1 15 



Classification and synonymy 118 



Atremata^ 119 



Telotreiuata 121 



Xeotremata 129 



Protreniata 131 



Diagram illustrating geologic distribution of families 131 



Synopsis of the divisions of Bracbiopoda higher than genera 136 



Chapter VI. Index aud bibliography of American fossil Brachiopoda 138 



