54 THE STORY OP THE EARTH AND MAN. 



JS^ow ia this enumeration we observe, in tlie first 

 place, a representation of all tlie lower or invertebrate 

 groups of tbe waters. We have next the remarkable 

 fact that the Radiata of Cuvier, the lowest and most 

 plant-like of the marine animals, are comparatively 

 slenderly represented, yet that there are examples of 

 their higher as well as of their lower forms. We 

 have the further fact that the crustaceans, the highest 

 marine animals of the annulose type, are predominant 

 in the waters ; and that in the moUusks the highest 

 and lowest groups are most plentiful, the middle less 

 so. The whole number of species is small, and this 

 may arise either from our having here reached an 

 early period in the history of life, or from our in- 

 formation being defective. Both are probably true. 

 Still, of the animals known, we cannot say that the 

 proportions of the different kinds depend on defec- 

 tive knowledge. There is no reason, for example, why 

 corals should not have been preserved as well as 

 Trilobites, or why Brachiopods should have been 

 preserved rather than ordinary bivalves. The pro- 

 portions, therefore, it may be more safe to reason from 

 than the aggregate. In looking at these proportions, 

 and comparing them with those of modern seas, we 

 are struck with the great number of species represent- 

 ing some types either now extinct or comparatively 

 rare: the Trilobites and Brachiopods more particularly. 

 We are astonished at the enormous preponderance 

 of these two groups, and especially of the Trilobites. 

 Further, we observe that while some forms, like 



