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our present knowledge ; the absence of the vertebrated 

 classes in the lowest strata being based upon strong 

 negative evidence. Of course it is possible that the 

 Vertebrata may have existed, from the earliest creation 

 of life, upon the earth ; yet not only have the most rigo- 

 rous researches of many years failed to discover a trace 

 of their remains, but, judging from the gradual develop- 

 ment or substitution of the vertebrated classes through 

 so many phases, until they assume such importance in 

 the Mammalia of the Cainozoic period, the conclusion 

 that such high types of life were altogether absent during 

 the first great life epoch appears strongly confirmed. 

 Notwithstanding the careful search that is constantly in 

 operation, several years have now elapsed without deve- 

 loping any new facts of importance tending to lower the 

 range of classes. The longer it continues we may the 

 more safely begin to trust the value of our conclusions, 

 and to assume that time will give them the character 

 of truth. 



In conclusion, we find the remains of the earliest 

 organic body that we are acquainted Avith is a Bryozoon.* 

 perhaps associated with Annelids. If these were the first 

 creatures that ever existed upon the earth, how interest- 

 ing to look upon their remains, and to find that they are 

 by no means the lowest animals in the scale of organiza- 

 tion. But have we really found such ? — or is it one of the 

 first traces of the spread of life from some distant centre, 

 Avhere the first creation unveiled itself in many classes, 

 perhaps even the entire invertebrata Avith which we 

 become acquainted as we ascend the Silurian system ; 

 the epoch that undoubtedly is the first great life era 

 that we can separate in geological sequence. After the 

 Bryozoa and Annelida, the first or lowest classes observed, 

 arc Zoophyta, Crustacea, and Brachiopoda ; and so far as 



* Oldliamia ladiata. 



