214 Revtezv of ''^ Outlines of the 



posited by successive inundations of salt and fresh water, 

 Tfae fresh water formations consist of marie, argillaceous 

 limestone and sand, traversed by veins of calcareous spar; 

 but they want the gypsum beds, so numerous in these 

 formations around Paris, and in wiuch are found the 

 bones of unknown birds and quadrupeds. 



The London Clay is an extensive formation in England, 

 and it is made up principally of a tough, bluish, or blackish 

 clay, occasionally marly, and embracing septaria, and beds 

 of sandstone, and green earth, which contain lime. It cor- 

 responds, probably, to the well known Calcaire grassier. o( 

 Paris. The organic remains in this formation are ex- 

 tremely interesting : among these are the crocodile, turtle, 

 several species of vertebral and crustaceous fish, numerous 

 testaceous molluscae, rarely a few zoophytes, masses of 

 charred wood, and many other vegetable remains. Mr. 

 Crowe procured 700 specimens of ligneous seed vessels in 

 one spot, none of which were duplicates. Mr. Defrance, 

 at a place near Grignon in France, found 500 species of 

 shells in this formation. Among Mr. Crowe's specimens, 

 are many which appear to have belonged to tropical cli- 

 mates. 



The Plastic Clay Formation is " composed of an indefinite 

 number of sand, clay, and pebble beds, irregularly alterna- 

 ting.'' It embraces a few layers of coal, fuller's earth, 

 some shells, teeth offish, vegetable remains, and it is said, 

 also, fossil bones. We have already suggested that this 

 formation not improbably exists in Martha's Vineyard, and 

 in several other islands along the coast of New-England. 



The Supermedial Order comes next m the descend- 

 ing series ; and comprehends the chalk, Beds between the 

 chalk and Oolitic Series, the Oolitic Series, and the forma- 

 tions between the Lias and the Coal Strata. These dis- 

 tinct groups of strata have many general relations and 

 analogies, that justify their arrangement into a distinct 

 class. One distinction between this and the Superior Or- 

 der, is, that in the latter, the organic remains are merely 

 preserved and not petrified ; while in the supermedial or- 

 der, they are all lapidified. The account of this order oc- 

 cupies nearly three fifths of the volume under considera- 

 tion. 



Chalk Formation. — This lies immediately beneath the 

 Plastic Clay : but a bed of debris, made up of rounded 



