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PROCEEDINGS OE THE GEOLOGICAL SOCIETY. 



demonstrated through his researches into the alum shale of Sweden ; 

 and the primordial fauna of Barrande has yielded Paradoxides, Cono- 

 coryphe, Agnostus, and Ellipsocephcdus, the first three of which are 

 characteristic British genera. 



Sweden has afforded P. Hichsii and other forms like our own. 



The Spanish primordial rocks yield genera identical with those of 

 our Menevian and Lingula-flags — Paradoxides, Conocoryphe, Ario- 

 nellus, and Agnostus. America, has its Acadian group, with Para- 

 doxides &c. The Protozoic schists of Bohemia (Eegion C, Barrande), 

 also contain Paradoxides (P. boliemicus), Sao, Conocoryphe, and 

 Agnostus. The same conditions prevail in Canada and New Bruns- 

 wick. It would thus appear that all the regions in Europe and 

 America north of 30° of latitude to the polar regions contain these 

 primordial rocks and fossils. 



I regard the Menevian of St. David's as being the most typical, 

 as regards both physical development and the abundance of organic 

 remains (individually and specifically). The intricacy of the geo- 

 logical structure of North Wales renders both the mapping and the 

 collecting of fossils in the Menevians there far more difficult than 

 in the St.-David's promontory, the strike of the beds being more 

 disturbed in continuity ; but I doubt not that an extensive fauna 

 is yet to be obtained from the Menevian of North Wales, where the 

 typical Lower Lingula-flags mantle round the still older Cambrian 

 masses. 



The palseontological value of any group of rocks can only be 

 arrived at through such analysis as I have here attempted to give ; 

 it is the census at a given time or age, and from such may be cast or 

 determined (approximately) the true and absolute value of the zoolo- 

 gical groups and their distribution through their respective formations. 



Plants. — No traces whatever of plant-remains have occurred in 

 the Menevian. 



Peotozoa. — The St.-David's beds of this age contain all the known 

 4 species of Protospongia, viz. P. diffusa, P. fenestrata, P. major, 

 and P. flabellata, the first three of which, as we have seen, are also 

 Longmynd and Harlech forms. At St. David's P. fenestrata passes 

 to the Lower Lingula-flags proper. None have occurred either in the 

 Menevian or Lingula-flags of North Wales. 



Hydrozoa. — No traces. 



Actinozoa. — Totally unrepresented. 



Echinodermata. — Cystidean remains were detected by Mr. Salter 

 in 1866 at St. David's; to these he gave the generic name Proto- 

 cystites. Dr. Hicks subsequently named these fragments P. mene- 

 vensis, after the horizon in which they occur. These obscure fossils 

 consist of arm-ossicles and body-plates ; it is the first Cystidean re- 

 corded. Dr. Hicks has also determined the presence of Dendro- 

 crinus cambrensis in the Tremadoc rocks of St. David's, the oldest 

 Crinoid known in the British rocks. 



Annelida. — Arenicolites didymus, Salt., A. sparsus, Salt., and Ser- 

 pulites fistula, Hall, appear to be all that are known of the Anarthro- 



