84 



«->tuar\. other animals inhabited the plains round the Sierra de la Ventana, and that 

 Lmmc streams acting together with the currents of a large bay, drifted their remains 

 towards a point where sand and shingle were accumulating in a shoal. The whole area 

 has since been elevated ; the estuary mud of former rivers has been converted into wide 

 and level plains ; and the shoals of the ancient Bahia Blanca now form low headlands on 



the present coast everything indicates a former state of tranquillity, during which 



various deposits were accumulating near the then existing coasts, in the same manner as we 

 may suppose others are at this day in progress. The only physical change, which we 

 kimw has taken place, since the existence of these ancient Mammalia, has been a small 

 and gradual rising of the continent*." 



* Fossil Mammalia of the Voyage of the Beagle, p. 11. 



