MARL AND SHELLS OF FRANCE. 429 



earthy parts of true marl are in a state of chemical combination 

 with each other, I am indebted to the " Essaisur la Harm" of M. 

 Puvis, which work, in an abridged form, I translated and published 

 in the third volume of the Farmers' Register. The author there 

 also states that the marls of France are principally, if not always, 

 of fresh-water formation, as is shown by the shells they contain be- 

 ing either such as belong to rivers and lakes, or to the land. This 

 is different from anything known in lower Virginia ; all our known 

 inarls, whether properly or improperly so termed, being deposits 

 made in a former sea, and the shells being those of sea-auinials.* 

 But though it is proper to describe that which only is truly 

 " marl/' before speaking of what is improperly so called, it is also 

 true that there is nothing to tell of the use of any true marl in 

 Virginia, and scarcely of its existence in the tide-water region. 

 I have as yet seen it in but few places, and there in thin layers 

 only, and then overlying ordinary beds of fossil shells, and inter- 

 mixed therewith. 



and with this, to constitute true marl, carbonate of lime is also combined, 

 forming a triple earthy compound, or perhaps a quadruple compound, if 

 including the small proportion of oxide of iron, which is a general or uni- 

 versal constituent part of all clays. 



* " It may be of some interest to scientific investigators to know more 

 particularly the shells of these marls of France. In a catalogue annexed 

 to the original ' Essai sur La Marne,' the author names the following shells : 



In a marl sent from St. Trivier yellowish, compact, of homogeneous ap- 

 pearance, and coming to pieces finely and easily in water 

 Land shell Turbo elegans. 

 River shells Helix fascicularis, Helix vivipara, f Helix teiitacula, f Mya Pic- 



torum. 



In a marl from Cuiseaux, Saone et Loire 

 River shell Melanopside (of Lamarck.) 



In a marl from Leugny, in Yonne 

 Land shell f Chassilie ridee (of Lamarck, and Draparnaud, fHelix lubrica. 



In a marl from St. Priest in Dauphiny earthy, yellowish, very easy to 

 crumble in water 

 Land shell fAmbrette alongee, of Lamarck and Draparnaud, f Helix hispida. 



In an analogous formation of marl, in the basin of the Rhone, between 

 Meximieux and Montluel, the Helix striee, a land species, is found in great 

 abundance." 



M. Puvis states that among these, and among all the species of shells 

 found in the marls of the basin of the three great rivers, Saone, Rhone, 

 and Yonne, there are no remains of sea shells. All seem to have been 

 formed under fresh water. "But (he continues) as these marls contain 

 land shells, often in great abundance, we. must conclude, that the revolution 

 which heaped up the marls, has been preceded by a time in which the land 

 was not covered by water, in which the earth producing vegetables, per- 

 mitted the multiplication of the species of land shells which were found in 

 these marls." Essai sur la Marne, p. 8 to p. 24, and translation in Farmers' 

 Register, iii., note to p. 692. 



j-Living species are still found in the same region similar to those marked 

 thus. 



