2io RAMBLES AND REVERIES. 



The imperfection of the geological record may be. 

 pleaded as an excuse for the absence of transitional 

 forms, but then, as Prof. St. George Mivart says, "it 

 is an excuse." When we reflect that the trilobite was 

 built up after an entirely different pattern from any 

 older or contemporaneous creature whose fossil re- 

 mains have come down to us, that it had essentially 

 different nervous, digestive, and circulatory systems) 

 and that it possessed highly complex eyes and other 

 organs of sense, it is certainly very extraordinary 

 that there should be no geological record of transi- 

 tional forms of even the minutest character to enable 

 us to trace the descent of this curious animal or to 

 discover its generic alliances with any previously 

 existing creatures. Sir J. W. Dawson does not 

 exaggerate when he observes in reference to trilobites 

 that " nothing short of a very large faith in the 

 imperfection of the geological record can suffice 

 to account for their evolution." (Chain of Life, 

 p. 80.) 



When we turn to the consideration of the after 

 history of the trilobite, we find that both Geology 

 and Biology afford a little help in discovering 

 structural relationships with other crustaceans. As 

 to the value of these similarities and affinities in 

 evolutionist speculations different readers will pro- 

 bably entertain different opinions. 



I have already pointed out the striking resemblance 

 which Belinurus, a fossil king-crab from the coal 

 measures, bears to a typical trilobite (Fig. 57). It was 

 during this geological period that trilobites became 

 extinct, and it is interesting to find a king-crab of 



