﻿I860.] 



MITCHELL OLD RED SANDSTONE. 



149 



counted at least eight forms of Crustacean tracks, indicating an assem- 

 blage at the time, on that ancient sea-beach, of creatures similar in 

 size and organization to their congeners preserved in higher beds of 

 the formation, namely the grey flagstones. Although the number of 

 limbs attached to these ancient Crustaceans may still be matter of 

 doubt, yet we have in their stone impressions such a character as 

 would, on the one hand, be made by a gigantic Pterygotus, and on 

 the other, such as would be made by a creature as small as the 

 Sandhopper of our present shores, besides various intermediate forms 

 corresponding with the remains found in the flagstones. From such 

 evidence (and we think it must be allowed) do we infer the existence 

 of a similar life throughout the formation, even when all trace of the 

 organism has itself perished. 



OLD EED SANDSTONE. 



Upper .... Holoptychius-beds of Moray, Perth, and Fife. 

 Middle .... Fish-beds of Cromarty and Caithness. 

 ( Conglomerate. 

 [Canterland Den.] 



Lower (10, 000 feet ^ 

 thick in Forfar) 



Grey flagstone with 

 intercalated sand- 

 stone. (" Cephal- 

 aspis-beds.") 

 [Canterland Den 

 (40 feet thick 

 here, 120 feet at 

 Carmylie), near 

 Farnell, &c] 



Gritty ferruginous 

 sandstone, with 

 occasional thin 

 layers of purplish 

 flagstone. 



[Canterland Den 

 (120 feet here 

 seen), Ferry den, 

 &c] 



Cephalaspis Lyellii. 

 Ichthyodorulites . 

 Acanthodian fishes. 

 Pterygotus Anglicus. 

 Kampecaris Forfariensis. 

 Vegetable remains, &c. 



Cephalaspis (in sandstone at Brechin). 

 Ripple-marks, Rain-prints, Worm- 

 markings, Crustacean tracks (large 

 and small, on the flags). 



Parka deeipiens (in the lowest grit*). 



§ 9. Some of the general conclusions to which the palreonto- 

 logical data seem to lead us may be stated as follow : — 



First, it must be granted that in these beds developed in the counties 

 of Forfar andKincardine in Scotland, and their equivalents in England, 

 we have the lowest members of the Old Red Sandstone. "We do not 

 venture to determine what those metamorphic rocks are upon which, on 

 the western side of our district, the Old Red Sandstone rests ; we leave 

 that point for future decision, either by the discovery of fossils in 

 some part of the Grampian chain or by the clear unfolding of their 

 stratigraphical relations. We hold, however, that the position of 

 the beds the palaeontology of which we have here endeavoured to 

 describe may now be held as fully ascertained. They are the foun- 



* And also in layers which alternate with coarse lower conglomerates on the 

 S.E. flank of the Grampians. — Edit. 



VOL. XVLT. PAET I. M 



