NOV gO IMO 



CONTENTS. 



lutroductiou Page 5. 



Geueral Remarlis upoii the structure of the Heliolitidse . 8. 



The uatiiral limits of the Heliolitidfe » 24. 



Distribution, geographical aud geological » 31. 



Ä s}'Stematic Synopsis of the Species described ,■ 35. 



Descriptions of Genera and Species > 38. 



Heliolites ■> 38. 



Cosmiolithus » 68. 



Probeliolites » 70. 



Plasmopora » 75. 



Propora » 87. 



• Caniptolithus » 99. 



Diploepora 102. 



Pyouolithus . 105. 



Coccoseris » 106. 



Protavrea » 109. 



Acantliolithus »112. 



Explanatiou of plates »115. 



Index v 139. 



