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EEA OF THE OOLITE. 



COMMENCEMENT OF MAMMALIA. 



TfiE chronicles of this period consist of a series of beds, 

 mostly calcareous, taking their general name (polite 

 System) from a consj^icuous member of them — the oolite 

 — a limestone composed of an aggregation of small round 

 grains or spherules, and so called from its fancied 

 resemblance to a cluster of eggs, or the roe of a Ush. 

 This texture of stone is novel and striking. It is supposed 

 to be of chemical origin, each spherule being an aggre- 

 gation of particles round a central nucleus. The oolite 

 system is largely developed in England, France, West- 

 phalia, and ISTorthern Italy ; it appears in Northern India 

 and Africa, and patches of it exist in Scotland, and in the 

 vale of the Mississippi. It may of course be yet dis- 

 covered in many other parts of the world. 



The series, as shown in the neighbourhood of Bath, is 

 (beginning with the lowest) as follows : — i, Lias, a set of 

 strata variously composed of limestone, clay, marl, and 

 shale, clay being predominant ; 2, Lower oolitic forma- 

 tion, including, besides the great oolite bed of central 

 England, fullers' earth beds, forest marble, and cornbrash; 

 3, Middle oolitic formation, composed of two sub-groups, 

 the Oxford clay and coral rag, the latter being a mere 

 layer of the woi-ks of the coral polype ; 4, tapper oolitic 



