A MONOGRAPH 



BRITISH FOSSIL CORALS. 



(SECOND SERIES.) 

 Part IV.— No. 1. 



INTRODUCTION. 



The Corals contained in the Liassic strata of Britain, France, Germany, and Italy 

 have a very decided community of fades ; at the same time it is evident that some 

 portions of the Liassic Coral-fauna resemble Triassic types, and that another portion is 

 allied to the Oolitic. 



This was to be expected, for it is evident that the stunted Thecosmilim, and the 

 Astrocanice of the Zone of Ammonites angulatus, are the descendants of the equally 

 stunted Tliecosmilice and of the Astrocwnice of the Triassic age. Moreover, the descendants 

 of the Isastrace, and of the larger Montlivaltim of the Lower and Middle Lias, luxuriated 

 in the Oolitic seas. 



The bulk of the Liassic Coral-fauna is, however, characteristic of and special to the 

 formation; and, as is the case in other great series of strata, certain assemblages 

 of species appear to characterise certain definite geological horizons. Yet not unex- 

 ceptionably, for some species range into higher zones in certain areas, whilst others, which 

 are confined to a definite horizon in one area, are found below and above the equivalents 

 of the horizon in a distant locality. Thus a species, which is only found in a particular 

 bed, and is associated with a particular molluscan fauna in one locality, may be found to 

 be associated with a molluscan fauna antecedent or posterior in its recognized succession, 

 in another place. 



It is this uncertain vertical range of species, this variation in vertical range in different 

 geographical areas, which causes the apparent antagonism of Physical Geology (as applied 

 to Classificatory Geology) and Palaeontology. 



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