29 



classification for formations, the names of those districts in 

 which they are either most prominently developed, or offer 

 especial facilities for study. A series of named land-marks is 

 thus obtained, by which the order of succession of the various 

 divisions is secured as they are determined one by one, and to 

 which reference may be made for the comparison of similar or 

 equivalent beds at long distances apart. The exact collation 

 with the defined systems of Europe will thus be facilitated, 

 and the nomenclature itself may at any time be converted 

 into the equivalent terms of that or neighboring countries in 

 proportion to the advances made in our acquaintance with 

 their fossil contents. 



In the same manner it may be convenient to speak of the • 

 Goal formation east of Fingal,, East Coast, Ac, &c., as the 

 Mount Nicholas beds, that being the spot where they are best 

 developed. The spiriferous lime-stones as the Mount Wel- 

 lington lime-stone, &c., <fec. 



As far as our information goes at present, the leading sub- 

 divisions of the Silurian formations may then be arranged as 

 follows : — 



1.. FiNGAL Beds 



/ Clay, Slates, \ 



) Sandstones, ( 



J and i 



[, Grits ; 



2. Eldon Valley 



3. GoBDoN Beds - 



Mud-stones 



and 

 Clay Slates 



Lime-stones 

 Slates 



Lime-stones 

 Conglomerates 

 Quartzose Sand 

 stones. 



No fossils have yet been^ 

 discovered 



Abundance of quartz reefs 



Tliin quartz 

 reefs not 

 abundant. 



}Calmyene "j 

 Orthis > 



Cardiola, &c. ) 



At some future period I shall enter in greater detail into 

 the component parts of- the above divisions, and their connec- 

 tion with each other. 



