Dr. H. Hicks — Life Zones in Pal(eozoic Rocks. 445 



orders, a greater number of genera, and, in the genera, show a 

 greater number of varieties or stages of progression, than we find 

 in any of the more Eastern areas. Many of these steps or species 

 are wanting in the Eastern areas, and it is probable that they never 

 reached so far, just as it is evident that many intermediate forms 

 did not reach the Western areas. Many forms, as they fulfilled their 

 mission, were lost on the way, and it is only the stronger and more 

 marked varieties, which we now look upon as species, that were 

 able to pass on. Minor changes may also have taken place even 

 in very limited areas ; but it is evident that the more marked species 

 were tolerably persistent and became more generally distributed." 

 It is a remarkable fact that all the evidence which has been accumu- 

 lated of late years tends to prove that there is a very close resemblance 

 between the succession of the sediments, and in the forms charac- 

 terizing the faunas of the Cambrian rocks on both sides of the 

 Atlantic Ocean. This seems to me to show, as I mentioned in my 

 paper in 1875, that the earliest homes of these faunas in this portion 

 of the northern hemisphere must have been in some intermediate 

 basin, whence migration took place towards each continent, and 

 it would also account for the larger number of species as we 

 approach towards this basin and for the diminished number in the 

 more distant areas. How far animal life had progressed, and how 

 many types were then in existence, it is impossible to say, for 

 those only which were suitable to the conditions then prevailing 

 in any given area would migrate to that part. The Zones of Life, 

 as we at present know them, are therefore mainly records of the 

 periods of dispersion of certain forms from areas previously occupied 

 by them. This is why our chronological sequence of organisms is 

 not more often in accordance with what the theory of evolution 

 may seem to demand. Generally the evidence of a gradual pro- 

 gression from lower to higher forms is clear enough ; but the 

 actual stages are not often found, owing to the probability that 

 none of the areas at pi'esent known to us retained the forms 

 sufficiently long, or supplied all the influences necessary, to produce 

 very marked changes in the animal forms. 



Upper Cambrian. 



In the very excellent summarj'^ of the researches carried on 

 in Wales given by Mr. R. Etheridge, in the Memoirs of the 

 Geological Survey, vol. iii. (1881),' it is stated that M. Barrande, 

 who paid a visit to this country in 1851 " for the express purpose of 

 comparing his rich materials with our published and unpublished 

 types," then recognised the " Lingula Flag " of Sedgwick as the 

 exact equivalent of his primordial stratum " (Etage C). At this 

 time the Middle Cambrian or Paradoxides fauna was entirely 

 unknown in Britain, therefore the Upper Cambrian or Olenus 

 fauna only could in any way be used for comparison. To M. 

 Barrande, therefore, must be given the credit of first recognising 

 the presence of this portion of the "Primordial zone " in Britain. 

 ' See also the Presidential Address to the Geological Society 1881. 



