Correspondence — Mr. R. L. Jack. 575 



P.S. — Mr. Bristow tells me that lie and Professor Eamsay found 

 Coal-measure sandstones with glacial striae in the Boulder-clay near 

 Cardiff, and that having seen the drift on Exeter Hill near Tiverton, 

 he remarked to Mr. Ussher, who was engaged in mapping the district, 

 that strise should be looked for, as polished gravel such as that was 

 very suggestive of glacial action. H. B. W. 



ME. HOPKINSON'S NEW SPECIES OF GRAPTOLITES FROM THE 

 SOUTH OF SCOTLAND. 



Sir, — While gratefully acknowledging the value of Mr. Hopkinson's 

 researches among the graptolites of the south of Scotland, I beg to 

 enter my protest against part of his paper in the November number 

 of the Magazine. 



At p. 501, Vol. IX., it is stated that " The Lanarkshire graptolitic 

 shale is considered by Prof. Geikie to form ' an upper .part of the 

 Moffat group,' but while decisive stratigraphical evidence is wanting, 

 from the evidence afforded by the fossils it seems more probable that 

 but one band of graptolitic shale runs through the Llandeilo rocks 

 of the south of Scotland, there being in this band several distinct 

 zones, each marked by a different assemblage of fossils, but with 

 many species in common." 



During the progress of the Geological Survey in the Leadhills 

 district, " decisive stratigraphical evidence " was obtained that the 

 Leadhills graptolitic shale group occupies a higher horizon than the 

 Moffat group. This is indicated in the Explanation of Sheet 15 of 

 the Geological Survey Map. 



Erom the localities given in Mr. Hopkinson's paper, it appears 

 that of the ten new species of graptolites described by him. two are 

 peculiar to the Moffat group, six peculiar to the Leadhills group, and 

 two common to both. There is not, here at least, much " evidence 

 afforded by the fossils " of the identity of the two groups. What 

 ■I object to on Mr. Hopkinson's part is his describing the whole ten 

 new species as "graptolites from the Moffat group," thereby mixing 

 up fossils which it is of the utmost importance to keep separate. 

 I am confident that neither Professor Geikie, nor either of my 

 colleagues, Messrs. Home and Skae, who have since the survey of 

 the Leadhills group carried on the work into the Moffat group, 

 would for a moment entertain the idea of their identity. 



Even where there really is an absence of stratigraphical evidence, 

 it seems to me that the best course is not to slump together all 

 the fossils collected within a certain area and call them a " group," 

 but to distinguish the fossiliferous rocks bed by bed, if need be. 



Of the localities in question a glance at Sheet 15 of the Geological 

 Survey Map will show the following to be in the Leadhills group, viz., 

 Wanlock Water, Kirk Gill, Lowen Dod, and Laggen Gill. Lochan 

 Burn, Erenchland Burn, Garple Linn, and Moniave (?) probably lie 

 within the limits of the Moffat group. I trust, therefore, that 

 pending the issue of the Geological Survey Memoir on the holew 



