T. G. Bonney. — On Supposed P kolas Burrows. 267 



recognized as belonging to this formation." From this quotation it 

 will be evident that the fossils found in the Millstone-grit shales of 

 Lancashire, have a totally different facies from those obtained from 

 the Sandstones of the Welsh border, the whole of the former, with 

 perhaps the single exception of the encrinital remains, are forms 

 belonging to and found in the Lower Coal-measures, and also more 

 sparingly in the subjacent Yoredale shales. 



Since writing the principal part of this paper, in looking about 

 for information on this subject, I have come across the observations 

 of Mr. J. H. Green, M.A., F.G.S., " on the Lower Carboniferous 

 rocks of North Wales," who it appears had arrived at a similar 

 conclusion, three years ago,' to that I had formed on independent 

 grounds as to the age of these rocks. I also notice that, in a section 

 accompanying a paper on " Paleeontological Observations on the 

 Limestones in Flintshire," by Mr. G. H. Morton, F.G.S., 156 feet 

 of the Upper Mountain Limestone is designated Yoredale series.^ 



Although I may not have been able to adduce evidence which will 

 be considered conclusive as to the Yoredale age of the rocks in 

 question, I trust I have succeeded in placing before the readers 

 certain facts calculated to show that the conclusions previously 

 arrived at are open to very grave doubts and serious objections, and 

 that, at all events, further and more decided proofs are necessary to 

 justify their retention as part of the Millstone-grit formation. 



IV. — On Supposed Pholas Burrows in Derbyshire. 

 By T. G. Bonney, M.A., F.G.S. 



DUEING a short vacation visit to Derbyshire I have had the 

 opportunity of making some further notes on burrows in 

 limestone rocks, which may be worth recording. These burrows, 

 it will be remembered, have been attributed by Messrs. Darbyshire,^ 

 Mackintosh,* and others, to the action of Pholades, a conclusion 

 which I ventured to oppose, after an examination of several instances 

 in the neighbourhood of Llandudno.^ Mr. Darby shire calls atten- 

 tion, in his paper, to the occurrence of these burrows near Buxton, 

 on Grin Edge and Harper Hill, at a height of about 1400 feet 

 above the sea. I was therefore fully prepared to meet with them in 

 the Carboniferous Limestone in other parts of the county. 



The first distinct case which I observed was in Millers Dale. I 

 descended into the valley, from the railway station, to the road 

 which runs along the northern bank of the Wye, to Litton Mills, and 

 is rarely more than a few feet above the water. Millers Dale in 

 this neighbourhood is clearly an instance of subaerial aqueous denu- 

 dation, a somewhat irregular example of the Y type of valleys ; the 

 lowest part being at times a well-marked gorge, with precipitous 

 sides, and bed but little wider than the existing stream. A short 



1 Geological Magazine, Vol. IV., p. 11. 



2 Transactions Liverpool Geological Society, 1868 and 1869, p. 75. 

 ^ Lit. and Philosoph. Soc. of Manchester, Memoirs, Ser. iii. vol. iv. 

 ■* Geological Magazine, Vol. VIL p. 47. 



* Geological Magazine, Vol. VL p. 483. See also Mr. Eofe's paper, vol. vii. p. 4. 



