a

. Alan Cutler, The Seashell on the Mountaintop (New York: Dutton, 2003).

“Nothing is so high, nothing is so far from the sea that we cannot find [shells] of those creatures that only live in sea water.”  Jan Van Gorp (1569), as quoted by Cutler, p. 59.

John Woodward, An Essay Towards a Natural History of the Earth (London: 1695; reprint, New York: Arno Press, 1978), pp. 3–74.

b

. During the period 1508 to 1515, Leonardo da Vinci carefully studied the shells he found high in the Italian mountains. He raised valid arguments against all the hypotheses that others were proposing to explain shells on mountains, but he offered no explanation of his own. [See Leonardo da Vinci, The Notebooks of Leonardo Da Vinci, Vol. 2, editor Jean Paul Richter (New York: Dover Publications, 1970), pp. 208–218.]