136 Dr Bone’s Geological Comparative View of the 
composed of triturated particles of organic marine bodies ; Ceri- 
thia, Echinites, &c. are found in it. The other variety is a true 
marly sand , of a greyish or yellowish colour, and containing shells, 
the species of which can be referred to sixty-three genera of La- 
marck, besides many Lunulites, Madrepores, and some remains 
of Cetacea, and even perhaps of quadrupeds, as of the Masto- 
don (Dax). These remains are distributed in these faluns irregu- 
larly, so that some fossils have their particular localities, and then 
they are very frequent. Many are similar to those of the cal- 
caire grossier of Paris.; but many also are like those of the Me- 
diterranean deposits, or are peculiar to the basin. This forma- 
tion occupies only the western part of the basin ; and the mid- 
dle part (Department de Lot et Garonne, &c.) is occupied by 
the fresh-water deposit which lies upon the molasse, and indi- 
cates its posteriority to the compact marine limestone, by a cu- 
rious alternation of a bed of fresh water limestone, with the falun 
at Saucas , and by the intermixture of Melanopsides, Helices, 
Planorbes, Neritines, in the upper part of the falun or sandy marl 
of Dex. These localities are in the place where the water of the 
fresh-water lake discharged itself into the sea. 
The plateaux of fresh-water limestone , consist of a thick bed of 
a compact white or yellow limestone , which is without shells, and 
which in specimens might often be confounded with Jura lime- 
stone, . although, in the great, the geologist easily discovers in it 
the characteristic pores and concretionary structure of a lake de- 
posit. The upper part is an ordinary cavernous fresh-water 
limestone, sometimes a little bituminous, and with the common 
shells of the Helix, Planorbis, and Lymnaea kinds, and fragments 
of bones of quadrupeds, (Palootherium). Some veins of barytes 
exist in the first, and some masses of millstone or coarse flint, si- 
milar to the Parisian, are imbedded in it, with fragments of sili- 
ceous w r ood. 
Upon this rock there rest marls and argillaceous clay, with 
nests of coclS s-comh gypsum , (gypsum en crete de coq), and a 
bed of marl with large oysters. At last we find the great sandy 
deposits forming the Landes, and existing over a vast extent of 
country. It is a pure quartzose sand, cemented here and there 
by hydrate of iron (Chalosse), and for that reason able only to 
rear pines and cork trees. In the Chalosse it is more marly, and 
