78 THE OLD RED AND CARBONIFEROUS PERIOD. CHAP. 



The Old Red Sandstone is seen on the west of the Abberley and 

 Malvern Hills, and on the west of Newent, where the new red 

 and old red systems meet on a line of fault, prolonged from the 

 Malverns toward Berkeley. In the wide region west of the Mal- 

 verns which extends to Pembrokeshire, the series of red and pale 

 green strata acquires a thickness of from 5000 to 8000 feet, and 

 consists essentially of three parts b . 



Upper part. Conglomerates with thin red marls, and sandstones : 

 e.g. the Vans of Brecon. 



Middle part. Thick laminated red sandstones with thinner 

 sandy red marls (a few greenish bands), and traces of cornstones : 

 e.g. about Ross. 



Lower parts. Thick red laminated marls and shales, variegated 

 with greenish bands and blotches, and beds and lumps of corn- 

 stone, and including many thin beds of laminated sandstone, some 

 of which are near the bottom. This group is the only one ob- 

 servable along or parallel to the ranges of Malvern and Abberley, 

 and is about 2500 feet thick. It rests, but perhaps not quite 

 conformably, on the subjacent Ledbury shales and Ludlow rocks. 



The organic remains are few, chiefly fishes of the curious genera 

 Cephalaspis, Pteraspis, and Scaphaspis. Very few marine shells c ; 

 no trilobites; no corals. Mr. Godwin Austen has expressed an 

 opinion that the deposit is of fresh-water origin. 



On comparing these two great systems of strata, remarkable 

 contrast appears in physical characters, probable origin, and organic 

 association. 



The comparison may be in a tabular form as under : 



SILURIAN. 



Protoxidated sediments prevail ; little 

 or no red oxide of iron ; much limestone 

 of coral and shell growth. 



Organic remains very numerous ; ex- 

 cepting fishes. 



Sea basins opening variously to the 

 east and north of Europe, and America, 

 between the Ural and the Rocky moun- 

 tains. 



OLD RED. 



Sediments rich in red oxide prevail ; 

 very little limestone, and that not coral- 

 loidal, and not shelly. 



Organic remains scarce, excepting fishes 

 of singular forms (e.g. Cephalaspidae). 



Basins (whether seas or lakes) of 

 limited extent, mostly detached or in 

 proximity to lately elevated land. 



b Memoir on Malvern, already referred to. 



c A small species of Lingula is found in the lower beds. 



