360 The Affietican Geologist. December, i898 
the sea or 40 feet above the river. The sections of Menche- 
court, Mautort, etc., are further distinguished from others at 
higher levels near Abbeville, and from all at both low and 
high levels along the upper part of the valley, by their con- 
taining marine shells. Lyell writes of their mode of occur- 
rence at Menchecourt as follows: 
In the lowest beds of gravel and sand in contact with the chalk, 
flint hatchets, some perfect, others much rolled, have been found; and 
in a sandy bed in this position some workmen, whom I employed to 
sink a pit, found four flint knives. Above this sand occur beds of 
white and siliceous sand, containing shells of the genera Planorbis. 
Limnea, Paludina, Valvata, Cyclas. Cyrena, Helix, and others, all 
now natives of the same part of France, except Cyrena [Corbicula] 
fluminalis, which no longer lives in Europe, but inhabits the Nile and 
many parts of Asia, including Cashmere, where it abounds. No species 
of Cyrena is now met with in a living state in Europe. Mr. Prestwich 
first observed it fossil at Menchecourt, and it has since been found 
in two or three contiguous sand-pits, always in the fluvio-marine bed. 
The following marine shells occur mixed with the fresh-water 
species above enumerated: Buccinum undatum, Littorina littorea, 
Nassa reticulata, Purpura lapillus, Tellina solidula, Cardium edule, 
and fragments of some others. Several of these I have myself col- 
lected entire, though in a state of great decomposition. . . . They 
are all littoral species now proper to the contiguous coast of France. 
Their occurrence in a fossil state associated with fresh-water shells 
at Menchecourt had been noticed as long ago as 1836 by MM. Ravin 
and Baillon, before M. Boucher de Perthes commenced the researches 
which have since made the locality so celebrated. The numbers since 
collected preclude all idea of their having been brought inland as 
eatable shells by the fabricators of the flint hatchets found at the bot- 
tom of the fluvio-marine sands. 
This part of western Europe was then slightly lower than 
now, indicating, with the absence of ice before noted, that 
the time represented by these sections preceded the great 
uplift of this region which culminated in the maximum Eur- 
opean glaciation. But earlier, and probably continuing with 
increased vertical and geographic extent during the early part 
of the Ice age, the general epeirogenic uplift of the continental 
area bridged the strait of Gibraltar and the center of the Med- 
iterranean sea from Tunis to Sicily and Italy, as shown bv 
Dawkins and Geikie, raising the land in both regions abotit 
2,000 feet higher than now, and affording a passage to the 
great African mammals. They also crossed where the shal- 
