542 r£j?Eft ORDOVICIAX OF THE BEEWYJi hills [vol. Ixxix, 



and accorded well with their distribution in the deeper parts of 

 the epicontinental seas where these conditions were best attained ; 

 in certain circumstances, however, similar conditions might be 

 found in quiet, shallow water. The world-wide distribution of the 

 graptolites certainly seemed to necessitate free communication with 

 the open ocean, though perhaps, again in exceptional circum- 

 stances, graptolite-shales might accumulate in areas where there 

 was only restricted communication. It might, however, be ex- 

 pected that the fossils would then exhibit some abnormality. 

 With regard to the Black Shales in Prof. Pugh's country, they 

 appeared to the speaker to belong very much to the same horizon 

 as those described by Mr. King (top of the JPleurograptus-linearis 

 Zonej, and that would seem to fit in better with the succession 

 than their relegation to a lower horizon, which would make it 

 difficult to see what represented the P. -linearis Zone. 



Prof. Pugh's discovery of the Diouide fauna of the Whitehouse 

 Beds was most interesting and important, as it afforded another 

 instance of the invasion of the Welsh area by the Scottish type of 

 Ordovician fauna. This had been first noted in the resemblance 

 of the fauna of Prof. Fearnsides's Derfel Limestone to that of 

 the Stinchar Limestone. There could be little doubt that the 

 Ashgillian fauna as a whole was derived from this Scottish type of 

 fauna, and therefore this discovery of Prof. Pugh's was a further 

 indication of the gradual spread of that fauna into Wales. 



Prof. O. T. JoJfES said that he did not entirely agree with the 

 idea that the graptolite-shales were deposited in lagoons, although 

 it was evident that they were laid down in shallow water. The 

 difference in the folding at different horizons showed that there 

 was much movement along the bedding-planes, especially of the 

 softer strata. The terms Ashgillian and Caradocian are not 

 yet sufficiently well known to allow of their general application, 

 and consequently it is preferable (in the existing state of know- 

 ledge) to use local names for the formations, as had been done bv 

 Prof. Pugh. 



The Seceetary read the following communication received from 

 Mr. E. E. L. Dixo>-:— 



'In 1910 I bad occasion to go through much of the literature on radiolarian 

 rocks, and, of course, came to the classic work of B. N. Peach & J. Home on 

 the Southern Uplands. I had been led to the conclusion that radiolarian 

 cherts of the thinly wedge-bedded, striped type were very shallow-water 

 (• lagoon ') deposits, not those of deep seas, and, for comparison, I was looking 

 for cherts of indubitably deep-sea origin. Those of the Southern Uplands 

 had been claimed to be such, and the association of the cherts there with 

 graptolite-shales was. if I remember aright (I speak without the book), held 

 to be confirmation of the deep-sea origin of both. But, as some of the cherts 

 were evidently (from the desci'iption) similar, in essential features, to those 

 of the Culm, which I believed to be lagoon-deposits, I was led to examine the 

 credentials of graptolite-beds. Their claim to be of oceanic origin proved to 

 be even less well- substantiated than that of the cherts, for the simple reason 

 that, whereas the widespread radiolarian deposits of the present day are 

 confined to deep seas, no recent formation corresponding without doubt to 



