Vol. 67.] FROM. THIS PARADOXIDES BEDS OF COMLET. 299 



change of faunas to which Prof. Lap worth called attention in 1891. x 

 It has received conclusive corroboration from the excavations of 

 1909 and 1910 for the British Association 2 in the isolated hill called 

 Robin's Tump, about half-a-mile south of Comley Quarry. 



The basement deposits of the Middle Cambrian are now found 

 in contact with : (1) the Grey Limestones yielding Protolenus, 

 Strenuella, etc. (in the Quarry liidge) ; (2) the Olenellus Limestone 

 yielding Callavia, etc. (in Dairy Hill) ; and (3) the underlying green 

 sandstones, some depth below their summit (in Robin's Tump), 

 and in this last there is undoubted evidence that the contact is 

 due to unconformity. 



The duration of the interval represented by the change of faunas 

 finds a parallel in the time required for the physical break. How 

 much of the life-history of this interval may be provided by the 

 fossils of the Mack Limestone is a problem that remains to be worked 

 out. 



General Conclusions. 



(1) An unconformity occurs at the top of the Lower Cambrian 

 rocks of Comley, which trenches somewhat deeply into that series 

 and cuts out any upper members that may have existed. 



(2) The highest of the Lower Cambrian beds at present known 

 yield what appear to be successive modifications of a fauna closely 

 allied to Dr. Matthew's Protolenus Pauna, and characterized in part 

 by the presence of several members of the genus Callavia. 



(3) Many of the trilobites of these beds are identical with, or 

 closely allied to, species which occur low down in the series in 

 America, and many hundreds of feet below the horizon of the 

 Olenelli with the tels on-like pygidia. 



(4) Inferentially it appears probable that, if these Olenelli ever 

 existed in Shropshire, their place is among the beds which are 

 missing by reason of the unconformity. 



(5) The beds (conglomerate and grits) immediately above the 

 unconformity contain several species of Paradoxides, and should 

 therefore be classed with the Middle Cambrian ; but the evidence 

 at present available is not sufficient to warrant a very close 

 correlation with any of the horizons of the typical sections of 

 Scandinavia. 



(6) After passing a considerable interval of unexplored ground, 

 we find a series of gritty flags with a fauna characterized by 

 Paradoxides davidis and containing a number of brachiopods which, 

 taken together, indicate a high horizon in the Middle Cambrian. 

 These flags are succeeded above, with apparently complete con- 

 formity, by a series of shales in which occurs a form almost 



i Geol. Mag. dec. 3, vol. viii (1891) p. 532. 



2 Rep. Brit. Assoc. 1910 (Sheffield) pp. 113-22, and MS. Rep. Brit. Assoc. 

 1911 (Portsmouth). 



Y2 



