X PREFACE. 



entire division of Tabulata, and, perhaps also, 

 the Rugosa, can no longer be associated with the 

 undoubted Actinoid polypes, but find, rather, their 

 true place in the neighbourhood of the genus 

 Hydr actinia. The details of these observations 

 having not yet fully appeared, it seems premature 

 to adopt the important systematic change thereby 

 indicated. 



