J. G. OoodcMld — The Coniston Limestone Series. 297 



building with a point a little to the north of the summit of Eomau 

 Fell. Both points can easily be kept in view. He will cross (1) 

 the Bunter Sandstones and Shales; (2) the Outer Pennine Fault, 

 which runs north-westerly along the upper side, of Helton Sike; 

 (3) the Coniston Shales, seen in several places on the Moor; (4) the 

 Ehyolite tuffs (Dufton Pike beds) of the Seat ; (5) a narrow strip 

 of the Milburn Rocks faulted in by the Middle Pennine Fault; (6) 

 the Helton Moor Volcanic Series, and also an interesting dyke of 

 microgranite, containing large rhombs of muscovite, like the Dufton 

 " Granite." These are best exposed along the 1250 feet contour. 

 When this is reached, the observer will see the rocks best by 

 following the same elevation southward. Their outcrop extends 

 over about seven hundred yards. These volcanic rocks will be seen 

 to have a fairly-steady, and high, northerly dip, so that lower beds 

 rise to the surface as the rocks are traced southwards. They consist 

 of alternations of ashy mudstones, ashy grits, tuffs, and a few beds 

 of lava, which occur chiefly at the north end of the exposure, and 

 are, apparently, of an andesitic type. One or two beds of lava are 

 markedly porphyritic, and recall the beds of Eake Brow, Melmerby 

 .(whose volcanic origin was demonstrated by the Survey in 1876). 



As the beds are followed towards the south, their base is reached, 

 and the volcanic rocks are seen to graduate downward into a group 

 of very calcareous and partly ashy-looking shales. I have published 

 references to this important piece of evidence on many previoiis 

 occasions, and have, in addition, had the pleasure of conducting 

 many fellow geologists over the rocks in question during the last 

 fifteen or more years. 



We are indebted to Messrs Marr and Nicholson for very valuable 

 lists of fossils from these beds. On account of the occurrence in 

 them of Trematis corona, the authors just named have called these 

 beds the Corona Beds. The name seems to me to be not altogether 

 a good one, and for the following reasons : — Trematis corona occurs 

 in the Coniston Shales in several localities. Below these shales 

 come the rhyolite tuffs, which are hardly less than 1100 feet in 

 thickness. Immediately beneath them the exact sequence is not 

 known ; but I do not think that any great thickness of rock (if any 

 at all) is missing. Then follows the series of volcanic rocks of 

 Helton Moor, just referred to, which are certainly not less than 

 1000 feet in thickness. (I more than suspect that these Helton 

 Moor volcanic rocks are the equivalents in time of those I named 

 the Rake Brow Series, from the place of that name east of Melmerby. 

 Certainly some beds very much like the Helton Moor beds occur at 

 the base of the series at Rake Brow; just as rhyolitic tuffs like 

 those of Knock come on above them.) Below the Helton Moor 

 volcanic rocks is the Lower Trematis corona bed, that is to say, the 

 fossiliferous shales mentioned above. 



I think if Mr. Marr had acted upon the friendly hint I gave him 

 in a letter some time back, he would have found that there are two 

 Corona beds here, and that these are separated by a considerable 

 thickness of other rocks, as Professor Lapworth informs me is the 



