126 



PROCEEDINGS OE THE GEOLOGICAL SOCIETY. 



Table IX. — Llandeih. 



Classes. 



Hantae. 



Protozoa , 



Hydrozoa , 



Actinozoa 



Echinodermata 



Annelida 



Crustacea 



Bryozoa. 



Brachiopoda 



Lamellibranchiata 



Gasteropoda 



Pteropoda 



Heteropocla 



Cephalopoda 



1 



18 

 3 

 4 

 6 



20 



10 

 5 

 6 

 1 

 3 

 3 



1 



44 

 3 

 4 

 9 



45 



34 

 6 



12 

 3 

 7 

 7 



175 



Geographical Distribution. 



Caradoc or Bala. 



The rocks overlying the Arenig and Llandeilo groups, and under- 

 lying the May-Hill Sandstone, have received much critical attention 

 from Sedgwick, Murchison, M'Coy, Salter, and the officers of the 

 Geological Survey. The facies of the fauna is that of the Llandeilo, 

 but greatly developed. The increased fauna of the Caradoc is 

 scarcely recognized until subjected to critical research and analysis. 

 The difference in the fossil contents of the two groups is due chiefly 

 to age and the conditions under which, they were deposited. Sedg- 

 wick, in 1853, placed the Bala group in his " Upper Cambrian " 

 division, dividing it into Lower, Middle, and Upper Bala ; it in- 

 cludes also the Cambro- Silurian of some authors, a term used or 

 adopted by Prof. Jukes in his ' Manual of Geology/ 



Prom the year 1832 to 1853 Sedgwick included the Caradoc in 

 the term " Lower Bala," not admitting then the existence of the 

 term Caradoc. Sir H. de la Beche, Prof. J. Phillips, and the Survey, 

 from 1840 to the present date, designate this formation the "Caradoc 

 or Bala." Murchison, from 1831 to 1859, used the term "Caradoc 



