TERTIARY AGE. 



Synopsis of the Animal Kingdom (exclusive of Annulata) during the 

 Seventh Cretaceous Period. 



452, Independently of some Saurians, fishes, Crustacea and 

 Annelides, found among the fossils, sixty-six species of Mollusca 

 and Radiata have been catalogued by M. D'Orbigny, of which 

 only two are common to this and the preceding period. Of 

 these, a considerable number, including the Nautilus Danicus 

 (figs. 9, 10, 11), are found in this stage in Sweden as well as in 

 France, and may be regarded as more especially characteristic 

 of the closing period of the Cretaceous age. 



The Tertiary Age. 



453. At an early date in the progress of the science, the strata 

 below the Jurassic formation were called primary, and the 

 Jurassic and Cretaceous formations, taken together, were denomi- 

 nated secondary, having been obviously deposited from the seas 

 of that era upon the former. Hence the most recently deposited 

 group of strata resting upon the Cretaceous formation, and im- 

 mediately subjacent to the diluvial and alluvial deposits of the 

 human period, received the name of Tertiary, which, by general 

 consent, they have retained, although subsequent discoveries have 

 shown that the preceding deposits, instead of being resolved into 

 two, are much more properly regarded as consisting of a greater 

 number of distinct groups. 



454. The strata composing the Tertiary formation have been 

 very variously classed, and grouped in geological works. Sir 

 Charles Lyell has divided them into three principal groups, which 



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