370 Br. H. Hicks — Life Zones in Palceozoic Rocks. 



Ganges, and which are only not as important as the Dudley Lime- 

 stone because they have been as yet less studied and described." 



It is sometimes stated that the work of correlation by the study 

 of the distribution of organisms in the strata received about this 

 time a severe check, not only because of the views ah'eady referred 

 to, but also owing to the doctrine of colonies, as propounded by 

 M. Barrande, and that this was especially the case with the Lower 

 Palseozoic rocks. Mr. Salter's remarks show clearly that he, at 

 least, was not unduly influenced by the wave of thought just then 

 affecting the geological mind ; and there is abundant evidence in the 

 many papers published about this time and subsequently on the 

 Lower Palaeozoic rocks of Wales to show that though the prevailing 

 views were given due consideration they did not in the least prevent 

 the facts obtained being always fairly stated and supported. 



In regard to Life Zones, which it has been stated were then 

 particularly neglected as being objects of distrust, I need only say 

 that so far as the Welsh rocks were concerned from the very com- 

 mencement of our work in 1863, the Life Zones were clearly 

 indicated, the range of each, species was given, and the organisms 

 supposed to be most typical of the zones and most useful for 

 purposes of comparison were always carefully mentioned. As 

 evidence bearing on this point I need only quote the following 

 passage from my paper, " On some undescribed Fossils from the 

 Menevian Group," in the Quart. Journ. Geol. Soc. May, 1872, 

 pp. 180, 181: "During my researches at St. David's I have, from 

 time to time, endeavoured to note the range of the genera and 

 species as they were discovered ; and the results have been given 

 in the several tables published in the Journal of the Geological 

 Society and in the British Association Reports. I have not, how- 

 ever, been able to obtain much evidence by this means to support 

 the theory of colonies propounded by the eminent palasontologist, 

 M. Barrande ; but several very interesting facts have been noted, 

 which it might be well again to refer to. The Brachiopods here, 

 as in other formations, have a greater range than any of the other 

 fossils, the same species extending in some cases through the whole 

 Cambrian series. The sponges come next; iov Protospongia fenestrata 

 occurs in the Longmynd group, in the Menevian group, and again 

 in the Upper Lingula flags, to the base of the Tremadoc rocks, 

 where it was found by me a few years since when examining these 

 rocks in North Wales. These, therefore, continued to live on during 

 the deposition of from 8,000 to 10,000 feet of strata. None of the 

 other Menevian species have any considerable range ; and but very 

 few of the genera pass beyond the Menevian boundary. Out of ten 

 genera of Trilobites, one only, the little Agnostus, passes upwards ; 

 and not one species out of the whole number, in all twenty-nine. 

 Indeed, the range of all the species is very limited ; and each one 

 seems to mark a special zone, where it flourished for a time and then ' 

 disappeared, perhaps to be followed by others of the same type but 

 never to re-appear. The Crustacea are, therefore, in these earliest 

 rocks, the surest indices of the age of the strata, and the best guides 



