All the land and fresh-water shells of the basins of Paris and Hampshire belong to extinct species. In Hordwell cliff' Mr. Lyell found viviara lenta, melania conica, melanopsis carinata, M. brevia, planorbia lens, P. rotundatus, Limneæa fusiforrnis, L. longiscata, L. columellaris, potamidutn margaritaceum, neritina, ancyhis elegans, unio solandri, mya gregarea, M. plana, M. subangulata, and 2 species of Cyclas. (Geol. Trans. 2d Series, vol. ii.)
The coeval beds of the Paris basin contain Cyclostoma mumia; Limnæa longiscata, L. elongata, L. acuminata, L. ovum, bulimus pusillus, &c.
Middle Tertiary Period.
In the upper fresh-water beds of the Paris basin (considered eocene by Mr. Lyell) occur many shells closely approaching recent species, as well as those of the true palæotherian age. The series is cyclostoma truncatum, C. elegans antiquum; Potamidum Lamarckii, Planorbis rotundatus, P. cornu, P. prevostinus; limnæa cornea, L. fabulum, L. ventricosa, L. inflata, L. cylindrus; Bulimus pygmæus, B. terebra; paludina carinata; Pupa Defrancii, P. muscorum; Helix lemana, H. desmarestina.
In the fresh-water limestone of Saucats, near Bordi aux (considered to be of meiocene date by Mr. Lyell and M. Deshayes, but ranked with later deposits by M. Dufrenoy,) are found Cyrena Brongniarti, Planorbis rotundatus, and Limnæa longiscata.
A strong analogy to existing as well as extinct species appears in the fresh-water deposits of Aix in Provence, where, according to Lyell and Murchison, the series of strata in descending order is as follows:—
150 feet of white calcareous marls and limestone, calcareous and siliceous millstone and resinous flints,—containing Potamidum Lamarkii, Bulimus terebra, B. pygmæa; Cyclas gibbosa, and another species.
The subjacent strata (marls, with fishes, plants, &c.) run out into a terrace, beneath which gypsum is exten-
