118 



has now sunk beneath the waves; and the inference becomes 

 conclusive, that tropical seas must have rolled over those existing 

 continents, amid whose mountain-chains the remains of ancient 

 Coral reefs are found. 



Ancient Coeal Eeefs. 

 A. Structure and Classification of Fossil Corals. 



As the study of all the known facts connected with the 

 Natural History of modern Coral reefs is necessary to a correct 

 appreciation of the probable conditions under which those of 

 past time were formed, I have devoted a greater space to the 

 consideration of this part of the subject than it was my intention 

 to have done when I commenced this paper ; however, these 

 observations are so numerous and important, and so interesting 

 and instructive at the same time, that I have ventured to 

 introduce them here even at the risk of being thought tedious. 

 The careful investigation of the modus operandi of modem 

 agents is indispensable to the right comprehension of those 

 which prevailed in ancient time ; for every thing concurs to show 

 that the past resembled the present, as the present is but a 

 continuation of the past : and the student who most cautiously 

 proceeds from the investigation of the known, to the study of 

 the unknown, is pursuing the only true method by which he 

 can hope to arrive at a sound induction respecting the conditions 

 under which phenomena of an analogous or identical nature 

 were produced in former periods of the earth's history. 



All the great epochs into which Geologists have divided the 

 fossiliferous rocks contain, in greater or less abundance, the 

 remains of the fossil skeletons of Actinozoa. Sometimes their 

 accumulation is so considerable, that strata of great thickness 

 and vast extent may be said to be composed of the extinct 

 forms of Corals; whUst the name commonly given to some 

 formations, as Coral beds, or Coralline Limestone, is sufficient 



