34 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [NoV. 19, 



of the Lower Silurian rocks. Another fossil is certainly an Ortho- 

 ceratite" *. 



I may further remark, that many of the singular forms brought 

 out on the surfaces of this limestone by weathering are probably, 

 as Dr. MaccuUoch long ago conjectured, of organic origin ; " in 

 particular the red vermicular forms very similar to many that occur 

 in the well-known marble of Babicomb." I have little doubt that 

 these are truly corals. Better and more determinable specimens 

 will probably yet be procured from some of the less altered beds of 

 this series ; but in the mean time the question arises, To what geo- 

 logical period do these organic remains belong ? What age do they 

 indicate for the beds in which they are found ? The only certain 

 genera are the Orthoceras and Euomphalus, but these characterize 

 rather the Palaeozoic beds in general than any of the formations in 

 particular. The mere resemblance of others to Lituites, Clymenice, 

 or Goniatites — to Silurian, Devonian or Carboniferous forms — is too 

 uncertain a foundation on which to build any argument. Beyond 

 the mere fact, therefore, that these formations belong to the great 

 series of Palaeozoic strata — and this fact is one of very high im- 

 portance, — I do not think that these organic remains will as yet 

 safely carry us. 



Distinctive physical characters. — Being thus, as it were, thrown 

 back on the general characters and relations of these deposits, the 

 question arises. Do they furnish us with any aid in determining 

 their age ? The red sandstone has hitherto been generally regarded 

 as of Devonian age ; and so strongly are the characters of this 

 formation, as seen in other parts of Scotland, impressed on it, that 

 we may affirm no doubt would ever have existed on the question, 

 except from its relation to the quartzite f . 



As it is now proved to lie below the quartzite, its age must evi- 

 dently be affected by our views regarding the latter rock, which, as 

 I have shown, is a distinct and newer formation. Now the close 

 analogy of this group to the mountain-limestone and associated sand- 

 stones, has forced itself on every observer, and in describing it com- 

 parisons with the coal-formation in the central districts of Scotland 

 constantly recur. The mineral characters of the beds are almost 

 identical — more so indeed than we might have expected, consider- 

 ing the distance of the localities and the changes the northern de- 

 posit has undergone. It consists of fine- or moderate-grained white 

 siliceous sandstones, not harder than many in Fife or the Lothians 

 in the vicinity of trap ; disposed in regular beds of moderate thick- 

 ness, with ripple-marked surfaces and false stratification ; of thinly 



* Brit. Assoc. Report for 1855, Trans. Sect. p. 87. In addition I may mention, 

 that'; a specimen of Orthoceratite, which I procured from these beds, measures 

 1*4 inch in length, with a diameter of '4 at the upper and "2 at the lower end. 

 It is somewhat compressed, and quite smooth on the external surface. 



+ Dr. MaccuUoch seems to have been inclined to regard it as a primary red 

 sandstone ; Mr. Cunningham named it " Transition." Professor Sedgwick and 

 Sir R. Murchison in 1828 classed some portions as " Primary," others as *' Old 

 Red." 



