222 Geology. 



that has been waged over them. But as our area has been 

 the chief scene of the battle-ground, it may be stated that, 

 formerly placed in a subordinate division of the Lias, they 

 are now admitted to a distinct place of their own, or are 

 placed on the top of the Keuper ; that the White Lias, so 

 named by William Smith, though it retains its original title, 

 has been relegated to the beds below ; and that the facies of 

 the fauna of this formation indicates a shore line and 

 brackish water \ whilst in Austria it is more of a deep sea 

 deposit. Amongst the characteristic shells are : — Pecten 

 Valoniensis, Modiola minima, Cardium Rhceticuvi, Pleuro- 

 phorus elongatus, Avicula contorta, Ostrea intusstriata, Crus- 

 tacea (Estheria minuta) ; Fish: — (Sargodon Tomicus and 

 Saurichthys acuminatus) ; Mammals : — (Microlestes anti- 

 quus or Moorei). 



Resting upon the " Sunbed " of Wm. Smith 



Lower Lias. 1-1 t e- n 



comes a thm band of yellow arenaceous 

 shale crowded with Ostrea Liassica, and here and there 

 dotted with fish scales. As this band, varying from one to 

 two inches in thickness, is persistent in our district and may 

 be traced wherever the White Lias is seen, it affords a good 

 datum line to mark the coming in of new conditions, — the 

 ushering in of the great age of Reptiles that must have 

 swarmed when the lower beds were laid down. The change 

 in colour and lithological character is very marked. The 

 white close-grained stone gives place to flaggy brown, earthy, 

 blue beds, with intermediate bands of yellow and blue clays, 

 the whole presenting a " ribbon-like appearance," layer upon 

 layer (hence probably the name of Lias given by the Somer- 

 set quarrymen) in continuous horizontal strata. The beds 

 vary in thickness from a few feet to 200 or 300 ft., and in 

 most of our local sections those beds whence the Saurian 



