140 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Feb. 25^ 



Fasc' p. 37), and is extremely common in the Coniston limestone 

 localities, and not found higher by you. 6. The Asaphus caudatus 

 of your list is not that upper species, but is totally distinct. It has 

 been described and figured {Odontochile ohtusicaudata, Salt, sp.) in 

 the * Camb. Fasc.,' p. 161, and is very common in the Bala lime- 

 stone and flags of Coldwell (Coniston group), and not known in any 

 higher position. 7. The Atrypa compressa of your list I found so 

 labelled in your collection. It has, however, no generic or specific 

 relation to that fossil, but is the Siphonotreta Anglica, Mar., the 

 only other known specimens of which were found in the Wenlock 

 shale. Therefore this fossil list, as now. examined, supports your 

 views ; for those (very few) upper Silurian species which were cor- 

 rectly identified from the first are well known to exist also in the 

 undoubted Bala beds and Caradoc shale with Trinucleus, Ampyx, 

 and other characteristic Cambrian forms." I may just remark that 

 Prof. M'Coy has in the first instance used the words Caradoc shale 

 incorrectly ; for I have never used these words to describe any black 

 shales (although such do sometimes appear) under the Caradoc 

 sandstone. The black shales north of Builth are undoubtedly a part 

 of the Llandeilo or Bala limestone group. *' As to the Orthoceras 

 Ibex (he adds), the specimens I have named in your museum prove 

 that it occurs, in my opinion, from the Upper Ludlow to the Conisto7i 

 limestone inclusive." These determinations had been made by Prof. 

 M'Coy, without a view to any previous hypothesis ; and seem also 

 to be conclusive as to the age of the Coniston flags. On this point, 

 he and Mr. Salter are in perfect agreement. 



Should I receive any new information during this spring respecting 

 the fossils of the Coniston grits, I shall rejoice to communicate it ta 

 the Society. But I have now no doubt respecting the true sequence 

 of the deposits between the central group of Cumberland and the 

 Old Hed Sandstone. The successive deposits, when arranged in the 

 following corrected order, agree physically and zoologically witb the 

 whole sequence of North Wales — Cambrian and Silurian. 



Ascending section from the centre of Skiddaw Forest to the Car- 

 boniferous Limestone near Kirkby Lonsdale. 



1 . Granite ; in some places sending veins into the overlying meta- 



morphic Skiddaw slate. 



2. Metamorphic slate ; near its base resembling, but never a true, 



gneiss ; quartz-rock ; mica-slate ; chiastolite in mass ; chiastolite- 

 slate gradually passing into a dark glossy clay-slate, &c. &c. It 

 is traversed near the granite by many poor metalhferous veins 

 containing abundantly many well-known Cornish minerals, such 

 as wolfram, schorl, apatite, &c. 



3. Lower Cumbrian group, or Skiddaw slate ; of very great thick- 



ness. Prevailing rock a dark glossy clay-slate that does not ef- 

 fervesce with acids. Many coarser beds, irregularly distributed, 

 very rarely as coarse as millstone grit. Fossils very rare — Fu- 

 coids SindGraptoIites. No shells found in it. 



