chap. xi. On the Thickness of the. 367 



these beds a mass of red calcareous clay, becoming in 

 the lower part more and more marly, containing layers 

 of sand, and of the thickness of 213 feet, was bored 

 through to a depth of 470 feet from the level of the 

 Rio Plata. This lower mass contained no fossils, and 

 its age is of course unknown ; l but I may add that I 

 saw at two points in Western Banda Oriental, beneath 

 the marine tertiary strata, beds of red clay with marly 

 concretions, which, from their mineralogical resemblance 

 to the overlying Pampean formation, seemed to indicate 

 that at an ancient period the Rio Plata had deposited 

 an estuarine formation, subsequently covered by the 

 marine tertiary beds, and these by the more modern 

 estuarine formation, with its remains of numerous 

 gigantic Mammalia; and that, finally, the whole had 

 been elevated into the present plains of the Pampas. 



Localities within the region of the Pampas where great bones have 



been found. 



The following list, which includes every account which I have 

 hitherto met with of the discovery of fossil mammiferous remains 

 in the Pampas, may he hereafter useful to a geologist investigating 

 this region, and it tends to show their extraordinary abundance. 

 I heard of and saw many fossils, the original position of which I 

 could not ascertain ; and I received many statements too vague to 

 be here inserted. Beginning to the south : — we have the two 

 stations in Bahia Blanca, described in this chapter, where, at P. 

 Alta, the Megatherium, Megalonyx, Scelidotheriurn, Mylodon, 

 Holophractus (or an allied genus), Toxodon, Macrauchenia, and 

 an Equus were collected ; and at M. Hermoso a Ctenomys, Hydro- 

 chaerus, some other rodents and the bones of a great megatheroid 

 quadruped. Close north-east of the S. Tapalguen, we have the 

 Rio ' Huesos ' (i.e. bones), which probably takes its name from 

 large fossil bones. Near Villa Nuevo, and at Las Averias, not 

 far from the Salado, three nearly perfect skeletons, one of the 

 Megatherium, one of the Glyptodon clavipes, and one of some great 

 Dasypoid quadruped, were found by the agent of Sir W. Parish 



1 It was supposed by Dr. Burmeister to be Silurian. 



