Occasionally, when the force of the river abated, marine shells of the genera Trigonia, Turritella, Pecten, etc.
"The Student's Elements of Geology"
Sir Charles Lyell
Pecten Beaveri, White Chalk.
"The Student's Elements of Geology"
Sir Charles Lyell
The presence among them of Lutraria rugosa and Pecten polymorphus, not known to range farther north in the actual seas than the coast of Portugal, indicates a somewhat warmer temperature at the time when they flourished.
"The Antiquity of Man"
Charles Lyell