50 MIDDLE CAMBRIAN XE1LOBITES. [March I913, 



Prof. W. W. Waits pointed out that phenomena of hrecciation 

 like those described by the Author were being recognized as of 

 frequent occurrence, especially in limestones. They were especially 

 well known in cornstones and in limestones of tufaceous character, 

 but they were also found in such well-bedded marine limestones 

 as those of the Carboniferous System. Hitherto, no general 

 explanation of the phenomena had been given. 



Mr. E. Greenlt, while admitting the possibility of con- 

 temporaneous erosion, thought that an unconformity was to be 

 expected at the horizon mentioned. Despite the thickness of the 

 Cambrian deposits of Carnarvonshire, the zone of Olenelhis had not 

 yet been detected. Cleavage, it was true, was strong ; but the 

 evidence now brought forward by the Author tended to confirm 

 the suspicion that the Olenelhis Zone might have been overlapped, 

 or even removed, by erosion along the slope of the old land, at a 

 very early period. 



The Author, in reply, said that there were phosphatic beds 

 among the Cambrian rocks of Comley which might mark pauses in 

 the sedimentation, but these were distinct from the breccias or 

 conglomerates. The breccias and conglomerates he regarded as 

 representing detritus from cliffs or islets, rather than as the result 

 of what was formerly called ' contemporaneous erosion.' The 

 older fossils found in them were furnished by the angular blocks, 

 and belonged to the Protolenus-Callavia Fauna, which, on the 

 analogy of American sections, occurred well down in the Lower 

 Cambrian ; Dr. Walcott had shown that the telson-bearing 

 Olenelli, which had not as yet been found in Shropshire, marked a 

 higher horizon than that of the Protolenus Fauna. 



The palseontological break between the Lower and the Middle 

 Cambrian of Comley, as described bj' the Author in a previous 

 communication to the Society, was very great, and was matched 

 by the physical unconformity which the excavations had proved to 

 exist in the district. This unconformity appeared to be just what 

 was required for the elucidation of the hiatus mentioned by 

 Mr. Greenly. 



In conclusion, the Author thanked the Fellows for their kindly 

 reception of his papers. 



