48 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Apr. 6, 



§ IV. — Conclusion. 



In the preceding pages I have (in the first place) endeavoured to 

 show that we find the true equivalents of the Tipper Lias Sands and 

 Cephalopoda-bed of the South of England in the Yorkshire coast ; for, 

 although the lithological features of this formation are somewhat 

 different in the north, still its palaeontological characters leave no 

 doubt as to the correlation of the Blue Wick beds near the Peak 

 with the Cephalopoda-beds of Gloucestershire. 



2nd. The chief object of this memoir was to demonstrate that the 

 Inferior Oolite admits of a subdivision into three zones of life, and 

 that each of these is characterized by certain species of Mollusca, 

 Echinodermata, and Anihozoa, which are special to it. 



3rd. That the zones are unequally developed in different regions 

 in England ; and the same remark applies to France and Germany. 

 The individual beds composing these subdivisions are sometimes 

 thin and feebly shown, or altogether absent in some localities, and 

 are more or less developed in others. The zone of Ammonites Mur- 

 chisonce is the one most frequently absent ; that of Ammonites Hum- 

 phriesianus has a wider geographical area ; whilst the zone of Ammo- 

 nites ParJrinsoni is the most persistent, and is frequently the only 

 representative of the Inferior Oolite formation. 



4th. That several Conchifera and a few Gasteropoda are common 

 to the three zones, whilst most of the Cephalopoda, Brachiopoda, 

 Echinodermata, Anthozoa, and Polyzoa lived only in one of these 

 subdivisions ; and that each zone contains a fauna of its own, which 

 sufficiently characterizes it. 



5th. That the zone of Ammonites ParTcinsoni possesses many species 

 of Mollusca, Echinodermata, and Corals in common with the Corn- 

 brash ; and the zone of Ammonites Murchisonce, several Conchifera 

 which lived in the Jurensis-stage of the Upper Lias; whilst the 

 Cephalopoda, Brachiopoda, Echinodermata, and Corals of the In- 

 ferior Oolite are all specifically distinct from those of the latter 

 formation. 



6th. The existence of three different faunas in the Inferior 

 Oolite is evidence that a long period of time elapsed during the 

 accumulation of this formation ; and the successive appearance and 

 extinction of so many different forms of Invertebrata testifies that 

 many important changes of level in the bottom, as well as in the 

 1 shore-line of the Jurassic sea, had taken place during the deposition 

 of the oldest member of the Lower Oolitic rocks. 



