534 Prof. C. Lapworth — On OleneUus Callavei. 



stimulus to future discussion, investigation, discovery and correc- 

 tion." It is somewhat instructive to note how — taking the publica- 

 tion of these provisional inferences as our starting point — geological 

 knowledge and opinion in this department has advanced in the 

 interval. These theoretical conclusions were three in number, and 

 for the sake of comparison — the contrasts between them (as para- 

 phrased from their original crude form), and their present aspect 

 (in so far as can be deduced from the actual state of geological 

 opinion), — may very briefly be summarized as follows : — 



{a) The presence of OleneUus in these Shropshire strata appears to fix the pre- 

 Cambrian age of the Uriconian Series of Dr. Callaway, and to render the pre-Cambrian 

 age of his Longmyndian a matter of fair probability. 



Since 1888, Professor Blake, who has of late years added very 

 much of great value to our knowledge of the Cambrian and pre- 

 Cambrian rocks, unhesitatingly assigns the lower zones of the 

 Longmynd Series of Callaway to his own Monian, or pre-Cambrian.^ 

 Sir A. Geikie, after studying the OleneUus -zone and the overlying 

 and underlying rocks in the field, has fi'ankly expressed his view 

 that the Uiiconian may be of pre-Cambrian age.^ Finally, the fact 

 brought forward in the present paper — namely that representatives 

 of all three divisions of the true Cambrian, as at present acknow- 

 ledged, are actually known to occur in Central Shropshire, being 

 mapped as constituting an integral part of Murchison's original 

 Lower Silurian, — renders it very unlikely that the Longmyndian 

 (the original pre-Silurian or Cambrian of Murchison and the other 

 great stratigraphists who immediately followed him) can be any- 

 thing else than pre-Cambrian. 



[b) The so-called Upper Cambrian of the Malverns, Central England and N.W. 

 Scotland may be in reality a greatly attenuated representative of the entire Cambrian 

 system ; part of an originally fairly continuous Cambrian once extending from 

 Lapland through Britain and Europe to Sardinia— and the Sardinian and Durness 

 formations may both range down to the base of the Cambrian. 



The recent brilliant discovery of OleneUus by the officers of the 

 Geological Survey of Scotland,^ in the Fucoid and Salterella zone, in 

 the lower parts of the Durness-Eriboll Series, establishes the correct- 

 ness of this suggestion for the N.W. Highlands. The detection of 

 Paradoxides Groomii in the supra OleneUus — infra Olenidian — zones 

 of Central Shropshire, as described in the preceding pages of the 

 pi'esent paper,* appears to settle the matter equally satisfactorily as 

 regards Southern Britain : — 



(e) If so the Torridon Sandstone of North West Scotland would possibly go with 

 the Longmyndian into the pre-Cambrian, the Schists of St. Lo in France, and the 

 rocks of corresponding antiquity elsewhere. 



Here, again, this provisional conclusion has been extended and left 

 far behind by later research and opinion. As already pointed out by 

 Sir A. Geikie," the discovery of OleneUus in the Durness-Eriboll 



^ J. F. Blake, On the Monian and Basal- Cambrian Eocks of Shropshire, Q.J.G.S. 

 1890, p. 386, et. seq. 



2 Sir A. Geikie, Anniversary Address, Q.J.G.S. 1891, pp. 86-90. 



3 Sir A. Geikie, Geol. Mag. 1891, p 449. 



* See ante p. 532. 5 Ibid. p. 449. 



