314 THE WOULD. 



inches across. The jaws are long and furnished with sharp coni- 

 cal teeth, resembling 1 those of the crocodile, and like them re- 

 placed continually, as they become worn, by new ones ; the fins 

 or paddles werofour. Both these remarkable animals, now en- 

 tirely extinct, are figured in the frontispiece of the present vol- 

 ume, which is designed to represent the condition of our globe 

 during the period we are now considering. 



Above the lias shales is a deposit which seems to indicate great 

 changes in the organic world, caused by the elevation of wide 

 tracts of country over certain portions of the globe, attended with 

 numerous depressions in other parts, and the strata deposited 

 during these movements seems to have formed the bed or final 

 depository of many successive races of beings. The name Oo- 

 lite given to this group of deposits signifies egg-like stone, be- 

 cause it is formed of small egg-like grains, like those comprising 

 the roe of a fish, the nucleus of which, on microscopic examina- 

 tion, appears to be some minute organic substance, usually a frag- 

 ment of coral, or a shell. To this class belong the so-called 

 Oxford and Kimmeredge clays, and the Jura limestone, since the 

 mass of the Jura mountains in France is of the oolite formation. 

 During this period, an immense number of marine animals flour- 

 ished, most of which are now entirely extinct, among them are 

 peculiar corals, star-fishes, and sea-eggs or echini. Below we 

 give a representation of a very perfect crustacean, similar to the 



lobster, from the oolite clay of Yorkshire, England. The fossil 

 remains of insects are also common in these strata, and very pe- 

 culiar and beautiful forms of ammonite, which seen?? to have 



