21 



it the lowest form of fossil. Since then, however, an im- 

 mense mass of strata had been found below this, containing 

 a small formation of genus fossil, which showed that it was 

 quite useless for scientific men to fix prematurely any limit to 

 their discoveries. This species to which he had referred 

 was called the Eozoon Canadetise ; it was found in limestone 

 of a highly crystalline character. Thus it could be 

 seen that the attitude of eveiy student of science should at 

 all times be purely tentative, as much apart as pos- 

 sible from the dogmatism which was the great 

 snare of scientific men at the present day. The 

 watchword of science was patience and humility, and 

 it was only as far as these conditions were observed, 

 that true success would be found. Dr. Mitchinson then 

 explained conformable and unconformable stratification, as 

 applicable to the succession of Silurian rocks. Upon the 

 Longmynd or Cambrian rocks lay conformably the first 

 truly fossiliferous strata, viz., the Lingula Flags, called by 

 the continental geologists the "Zone primordial," and 

 forming tke true base of the Silurian system. The Lingula 

 was merely a bivalve shell, belonging to the order in zoology, 

 called the Brachiopoda. This was one of the oldest forms 

 which existed in the ocean, but is to be found to this day 

 on our own Southern coast. It had little calcareous matter 

 in its shell, which was horny in texture, that primeval sea 

 apparently containing little carbonate of lime ; but 

 when we get to the limestone beds, there we find that life 

 was getting more largely developed, and then we get a pro- 

 fusion of animal remains. In the Lingula Flags, there are 

 a few species of Trilobite, an animal which the lecturer de- 

 scribed on the black boardandby moansot an engraving. This 

 trilobite belonged to the class Crustacea, and was somewhat 

 like tlic wood louse. It was derived from tres three, and 

 lobos a lobe, because it was divided into three lobes, with 

 two very large eyes, something like those of a fly. Upon this 

 reposed the whole of the Silurian system. Dr. Mitchinson 

 then exhibited some very fine specimens of fossils— par- 

 ticularly the trilobite of the Llandilo flags, the Ogygia 

 Uuchii— one of the characteristic fossils of the lower Silurian 



