130 The Rev. \V. Conybeare on the 



chalk, as seen in the Isle of Wight and Isle of Purbeck, which are 

 distinguished from the higher beds of the same formation by their 

 very superior consolidation. It is impossible for any two portions 

 of the same formation to be more entirely identified, by every 

 external character and by the fossils and organic remains contained 

 in them, than are these Irish beds, which have been frequently called 

 white limestone, with the English chalk in the above places : there as 

 in England the lowest beds are destitute of flints which the upper 

 contain in abundance. 



2. Mulattoe, an arenaceous stone, with a calcareous [cement, 

 of a speckled appearance (whence its name) derived from numerous 

 disseminated spots of green earth. It agrees altogether rn its cha- 

 racter and fossils with the green sandstone, which occurs in a 

 similar geological position underlying the chalk in England : the 

 thickness of this deposit appears to vary very considerably, and 

 has not in any instance been precisely ascertained. 



The numerous beds of coarse calcareous oolites, which in Eng- 

 land succeed this green sandstone, are entirely wanting in Ireland, 

 and the mulattoe reposes immediately on the lias limestone. 

 Analogous circumstances are not however wanting in England. 

 In the neighbourhood of Lyme Regis, in Dorsetshire, the green 

 sandstone has extended itself over the outgoings of the oolites, 

 rests upon the lias in a manner similar to that just described ; 

 and as it is covered with beds of chalk, the whole section affords 

 an exact counterpart to that presented by the Irish series. 



3. Lias Limestone, a blue argillaceous limestone disposed in 

 thin beds, alternating with slate clay, and distinguished by the am- 

 monites, gryphites and the remains of the pentacrinus, which it 

 abundantly contains. It may be worthy of remark that the sec- 

 tions given by Guetard and Monnet in the Atlas Mineralogique de 

 la France, and the accompanying description, clearly prove the 



