TRANSACTIONS OF THE SECTIONS. 93 



stand uncontroverted, Mr. Page went on at length to establish his proposed groups 

 of the lower systems. The yellow sandstones of Stratheden and Elgin, characterized 

 by such fossil forms as Pterichthys hydrophilus and Holoptychius Andersoni, Glypto- 

 lepis, Actinolepis, Stagonolepis, Telerpeton Elginense, and Cyclopteris Hibernicus, were 

 at once clearly separable from the carboniferous system above ; and it is likewise 

 readily distinguished, lithoiogically as well as palasontologically, from red marls, 

 sandstones, and conglomerates which lay below. These red beds were comparatively 

 barren of fossils, but perhaps the Holoptychius nobilissimus, Pamphractus, Glyptopo- 

 mus, and Phyllolepis, were their characteristic fishes ; at all events they marked the 

 meridian of the Holoptychius nobilissimus, whose scales were found in every district 

 where these red sandstones occurred. The Caithness flags, replete with such forms as 

 Pterichthys Milleri, Coccosteus, Dipterus, Diplopterus, Diplacanthus, Cheirolepis, 

 Osteolopis, and Asterolepis, were evidently a distinct group from the red sandstone 

 above, and as well defined on the other hand from the Forfarshire flags and tile- 

 stones, with their Cephalaspis, Onchus, Climatius, Parexus, Pterygotus, Kampecaris, 

 and other Crustaceans, as well as with their peculiar stems, seed-vessels, and unde- 

 termined flora. If the Caithness flags were not in some respects the chronological 

 equivalents of the middle flags of Forfarshire, they certainly did not hold a lower 

 place, and he was strongly impressed with the belief that the Forfarshire lower flags, 

 ■with their curious crustaceans, fish spines, fish jaws, and seed-spores, brought the 

 palaeontologist to the same geological horizon as the Ludlow Silurians. At this 

 stage there was yet an undetermined gap in Scottish lithology, and he was con- 

 vinced that it would shortly become a question whether portions of these old red 

 flagstones should be ranked as Upper Silurians, or the "tilestones" of Upper Silurian 

 replaced again as the natural basis of the Devonian system. Without attempting 

 any decided line of demarcation (and in a science like geology, where so many of its 

 arrangements were provisional, it was better that all sharp lines of demarcation 

 should be avoided), he was inclined to argue for the restoration of the " tilestones " 

 to the Devonian system, as bringing the Enghsh strata more in harmony with their 

 Scottish equivalents, and at the same time establishing for the Devonian that great 

 basis of vertebrate life for which Sir Roderick Murchison had so long contended. 

 Respecting the subdivision of the Silurian rocks of the south of Scotland (for in the 

 north no certain indications of Silurian fossils had been yet detected), Mr. Page was 

 inclined to accept the grouping suggested in the recent ' Siluria ' of Sir Roderick 

 Murchison. At all events, there could be no doubt in the mind of any one who had 

 worked out a stratigraphical section, and this altogether independent of fossil testi- 

 mony, that the grey wacke grits and schists of Peeblesshire, Selkirk, and Roxburgh, 

 •were older than the Silurian limestones, flagstones, and sandstones of Ayrshire and 

 Upper Lanark. Accepting the former as the equivalents of the Lower Silurians of 

 England, and the latter as representing the middle beds, there were still wanting, or 

 undiscovered, if it did exist, a set of strata corresponding to the Ludlow or Upper 

 Silurians. Leaving this uppermost stage as undetermined in the meantime, he next 

 proceeded, in descending order, to the metamorphic strata. It had been contended 

 by some that it was impossible to group or separate into anything like chronological 

 stages the metamorphic rocks ; and yet those who expressed such opinions were 

 themselves daily placing mica-schist under clay-slate, and gneiss under mica-schist. 

 There could be no doubt, that in greatly disturbed districts, and in regions where 

 these rocks had undergone a high degree of mineral metamorphism, it was often im- 

 possible to establish anything like order of superposition ; still, by taking a sufficiently 

 wide field, such as both slopes of the Grampians afibrded, and by working out 

 patiently many sections in detail, he thought there could be little doubt that the 

 following was the true descending order of the metamorphic strata in Scotland : — 

 1st. clay-slate, with and without slaty cleavage ; 2nd. chloritic and micaceous 

 schists ; 3rd. quartz rock and hornblende schists, forming, perhaps, one of the best 

 marked zones in the system ; and 4th. gneiss, porphyritic gneiss, and gneissose beds, 

 often so granitic-looking, that they were apt to be mistaken for granite, and for which 

 he would propose the term "granitoid schists." Though chlorite slate might, in 

 some instances, be associated with clay-slate, and mica-schists be intercalated with 

 gneiss, still, as a general rule, the preceding order prevailed ; and what was peculiar, 

 each zone had its own limestone beds, and these so persistent in character, that he 



