58 



LIFE ON THE EARTH. 



classes vary so as, in this limited sense, to justify our 

 speaking of different systems or combinations of 

 life ; but they are all included in one general plan of 

 the Omniscient mind, comprehending the past, the 

 present, and the future. 



Perhaps this subject may be yet further illus- 

 trated by means of tables shewing on the one hand 

 the numerical distribution in time of some genera of 

 marine animals now living and remarkably prevalent 

 in the sea, and of others as abundant in the more 

 ancient strata. In each case the relative abundance 

 of species is intended to be shewn by the numerals 

 corresponding to each period. I confine the illustra- 

 tions to the Molluscous animals, because of their 

 being the most uniformly plentiful in all periods, 

 and to the British Islands, as affording the best or 

 most convenient terms of comparison. 



Nwmerous in a living state. 



