In Silurian and Devonian Epochs 



lOI 



beds, gradually Increase in importance until they attain their 

 maximum development in the beds immediately underlying 

 the Old Red Sandstone. The rich brachiopod-fauna charac- 

 teristic of the lower beds dwindles and almost dies out with 

 the approach of shallow water conditions, although the 

 molluscs are somewhat more persistent." 



"The recurrence throughout of conditions tending to 

 the formation of "Bone Beds" is also worthy of note, such 

 conditions having prevailed at four distinct times at least 

 during the deposition of the rocks." 



As it is of importance here to compare the different 

 classifications of strata, and the views held regarding the 

 relation of the enclosed organisms of these strata, we ap- 

 pend the tables of Elles and Slater. 



PURPLE-RED SANDSTONES AND MARLS OF THE 

 OLD RED SANDSTONES. 



III. 



Temeside 



Group. 



II. 



Upper Ludlow' 

 Group. 



Temeside 

 or 

 Eurypterus 

 Shales. 



E. Downton-Castle 

 or 

 Yellow 

 Sandstones. 



D. Upper Whitcliffe 

 nr 

 Chonetes Flags. 



/. Gray carbonaceous grit — Fragment- 

 Bed, 

 e. Olive shales with Eurypteridae. 



d. Temeside Bone-Bed. 



c. Olive shales with Eurypteridae. 



b. Gray micaceous grit. 



a. Variegated shales and marls, 

 L greenish sandstones at base. 



e. Micaceous sandstones with fish- 



band and a few Lingulae. 

 d' Carbonaceous sandstones. 



c. Massive yellow sandstones, with 



Lingiila minima. 



b. Plat>chisma Bed, passing laterally 



into a Bone-Bed — ( D o iu n to n 

 Bone-Bed) . 



a. Unfossiliferous sandy shales. 



c. Ludlo^v Bone-Bed. 



b. Calcareous shales and flags with 



Spirifera ele'vata. 

 a. Calcareous olive flags with Cho- 

 netes elevata. 



C. Lower Whitcliffe { b. Concretion-Band. 



or Rhynchonella■^ a. Calcareous blue flags with Rhyn- 

 Flags. I chonella nucula. 



I. 



Aymestry 

 Group. 



B. 



Mocktree or j 

 Dayia Shales. / 



Shales and limestones full of Dayia 

 navicula. 



^. Aymestry or Con- (Massive limestones with Conchidium 

 chidium Limestone. I knightii. 



