676 oreneletts-zone of the north-west highlands. [nov. 1 894, 



Discussion. 



Dr. Hicks said ifc was highly satisfactory to find that such 

 important additions had heen made to the Olenellus-f&waa of the 

 .North-west Highlands. He would have liked to hear further details 

 than could he given in the abstract just read, especially as to 

 whether the new species marked distinct zones or whether they 

 occurred together. In the Paradoarides-be&s in South Wales, the 

 new species did not occur together, but were separated by various 

 thicknesses of beds. Where the deposits were sandstones the range 

 was much greater than where they were made up of finer materials. 

 The Olenellns-'ione at St. David's was separated by over 800 feet of 

 6andstone beds from the lowest Pa?-adoxides-zone, and the latter by 

 nearly 2000 feet of strata from the highest Paradoorides-zone. There 

 were no less than five distinct zones, each marked by a new species. 

 He had found it necessary from the first, more than 30 years ago, 

 to mark the zones with great care, and it was by that means, when 

 working afterwards in North Wales, that Mr. Salter, Mr. Homfray, 

 and himself were able to correlate the various subdivisions with 

 those at St. David's. He further said that in 1875 he prepared 

 a map, which is published in the Quart. Journ. of the Society 

 (vol. xxsi. pi. sxvii.). In that map he gave the distribution of the 

 Cambrian and Lower Silurian faunas over the European area, and 

 he stated in the paper which it illustrated that he thought the 

 migrations were from the Atlantic in a north-easterly direction 

 over Europe, and in a north-westerly direction over America. 



Dr. G. J. Hlnde also spoke. 



