GEOLOGY. 399 



ranges. We may here remark that the animals delineated in Plate 

 IX. ; several of them restorations from the skeletons, are all of genera 

 which are now extinct. :;: .; .; 



Next above the transition strata, are the secondary rocks ; which 

 include numerous organic remains, and comprise the principal beds 

 of coal and salt ; hence giving rise to salt springs. The organic re- 

 mains in the lower secondary rocks, including the old red sandstone, 

 carboniferous limestone, and coal formations, are chiefly vegetable ; 

 and were doubtless buried there, for the most part, by the gradual 

 accumulation of earthy materials. It is now very generally admitted 

 that all mineral coal, both anthracite and bituminous, was produced 

 from vegetable matter, deposited in beds, perhaps, of former lakes, 

 and afterwards subjected to subterranean heat. The coal measures, 

 containing beds or seams of coal, consist chiefly of sandstone, and 

 slate or shale, with ironstone, or ore ; but sometimes of limestone. 

 Above the coal formations, are the new red sandstone and magnesian 

 limestone ; the former sometimes associated with rock salt, or gyp- 

 sum : next come the lias and oolite, both composed of alternating 

 strata of clays and limestones, with some slates ; the former named 

 from its being in layers ; the latter, from its containing rounded 

 granules, like eggs : and highest among the secondary rocks are 

 compact formations of clay, sand, and chalk, including the Weald clay, 

 and green sand of England, containing numerous organic remains. 

 The lower secondary rocks contain rare remains of vertebrated fishes, 

 as the cephalaspis, (Plate IX. Fig. 6.) ; and some reptiles, as scorpi- 

 ons ; but chiefly shells and plants. In the new red sandstone, are 

 found the palaeoniscus, (Fig. 7.), the plesiosaurus, (Fig. 8.). the 

 ichthyosaurus, (Fig. 9.), and the pterodactylus, (Fig. 10.) ; besides 

 some slight traces of quadrupeds and birds. In the Wealden rocks, 

 Dr. Mantell found the remains of the iguanodon, (Fig. 11.), which 

 in some specimens was nearly 70 feet long. The secondary rocks 

 are often broken through, and overlaid, by unconformable masses of 

 basalt : and, in a few instances, porphyry, and even granite, appear 

 to have been thrown up like lava, through fissures from below. 



Next above the secondary, are generally found tertiary, rocks, con- 

 sisting of various deposites, of soft sandstone, limestone, gypsum, 

 sand, clay, and marl ; which last is chiefly a mixture of clay and car- 

 bonate of lime. These strata were apparently formed in bays, or lakes, 

 and hence are of limited extent. The lower series contain numerous 

 marine shells ; while some of the upper contain, in a few localities, 

 fresh-water shells, and the bones of quadrupeds and birds, often of 

 extinct species ; and these sometimes alternate with strata of marine 

 formation. Here we find the remains of the anoplotherium, (PI. IX. 

 Fig. 12.), the palaeotherium, (Fig. 13.), the dinotherum, (Fig. 14.), 

 the megatherium, or megalonyx, (p. 379.), and the mastodon, or 

 mammoth, (Fig. 16.), all of which races are now extinct. Above the 

 tertiary formations, we find strata of gravel, sand, clay, and shells, 

 mingled with large boulders, or rounded masses of rock, which have 

 evidently been transported from their original position, directly or in- 

 directly by the action of water. These strata have hence been called 

 diluvial; and they contain remains of the animals last named as well 



