314 



OUR COMMON BRITISH FOSSILS. 



open, reveal the coiled-up ringed shell, wonderfully 



resembling a snake in such species as Ammonites 



communis^ and still more wonderfully resembling one 



when they put a " head " on, with 



eyes in — as they sometimes do. 



Zones of Ammonites also occur 

 in the Oolitic rocks, both of Eng- 

 land and Scotland, as those of A. 

 Calloviensis, etc. In Scotland there 

 is an extensive outlying series of 

 Liassic and Oolitic beds, as in 

 Skye, and other islands, and in Sutherlandshire — 

 remnants of a vast sheet of Secondary strata which 

 probably once completely covered the Western High- 



Fig. 216.— Ammom'ies 

 varicostts. 



Fig. 317. — Ammonites CooI>ert. 



lands, where they have long been removed by de- 

 nudations. In the Oolitic strata of Sutherland an 

 impure coal is worked, as at Brora, and there the 



