550 MANUAL OF NATURAL HISTORY. 



II. — Old Red-Sandstone Group, 

 This is a marine formation, composed of strata of 

 marls, limestone, micaceous and gray sandstones, 

 conglomerates, quartzose grits, crystalline limestone, 

 and green slates ; the prevailing colour of all being 

 a dull red, derived from sesquioxide of iron. 



In Britain this group is well represented in 

 in the South of Devon, in Orkney, Caithness, 

 and Cromarty ; in Germany in the limestones 

 of Eifel ; in Russia, in a wide area south of St. 

 Petersburgh ; and in the United States, at the Falls 

 of the Ohio. The Tilestone division is composed of 

 finely laminated, hard, reddish, or green, micaceous 

 quartzose sandstones, with occasional beds of red- 

 dish shale. The Gornstone division consists of red 

 and green, argillaceous, and spotted marls, with 

 alternating bands of sandstone, and with irregular 

 courses of mottled, red and green cornstone, or im- 

 pure limestone. The upper portion comprises the 

 Quartzose Conglomerates and Sandstones; com- 

 prising quartzose-grits, and reddish quartzose con- 

 glomerates, passing into reddish coarse - grained 

 sandstones, with alternating layers of red and green 

 argillaceous marls. The Old Red-Sandstone is a 

 marine formation, and is especially remarkable for 

 the fossil fishes it contains, entire skeletons of ga- 

 noid and placoid families having been discovered. 

 A solitary reptile has recently been brought to light 

 by Mr. Duff, from the Elgin Sandstone, which ap- 

 pears to possess a mixed character between the 

 Amphibians and the Saurians ; it is the Telerpeton 



