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Fossil Beds of Shells

In beds formerly quarried for lime at the Calera de Arriola – a little off the road from B. Ayres to San Isidro are almost entirely composed of an Estuary Shell ─ the Potomomya of Sowerby the living type of which is figured & described by Maton in the Linnean Transactions as now found at the mouth of the R. Plata:─ at the junction of the fresh & salt water from which these preserved fossil Beds are now say 150 miles intact.─

Proof that here was once the mouth of the River (above Buenos Ayres) ─

p. 20 of Pampas Tombonbon

Below

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{one of the specimens, [shoal] of mere broken [heaps] of shells ─ crystalline-like Entre Rios = P. Gordon

The others with rounded fragments like Potomomya ─ ⸮ mactra?

X++ {Are the S. Isidro shells in rock?? are said to be quarried ─

= localities given with specimens = Height