Letter, 'Regarding the relative periods at which the different families of testaceous animals appear to have been created, and on the gradual approximation which may be observed in our British strata from the fossil remains of the oldest formations, to the living inhabitants of our land and waters' from L W [Lewis Weston] Dillwyn to Sir H [Humphry] Davy Subject: Palaeontology / Biology Published in Philosophical Transactions as 'A letter from Lewis Weston Dillwyn, Esq. addressed to Sir Humphry Davy, Bart. P. R. S'. Written by Dillwyn at Penllergare [Penllergaer, Wales]. Read 25 March 1824. 1 February 1824