324 Pampean Formation. pari h. 



directions ; they include an extraordinary number of 

 bones of gigantic mammifers and many shells. The 

 pebbles are of considerable size, and are of hard sand- 

 stone, and of quartz, like that of the Ventana : there 

 are also a few well-rounded masses of tosca-rock. 



Xo. 29. 



Section of Beds with Recent Shells and Extinct Mammifers, at Punta Alta in 



Bahia Blanca. 





The second bed (B) is about fifteen feet in thickness,, 

 but towards both extremities of the cliff (not included 

 in the diagram) it either thins out and dies away, or 

 passes insensibly into an overlying bed of gravel. It 

 consists of red, tough clayey mud, with minute linear 

 cavities ; it is marked with faint horizontal shades of 

 colour ; it includes a few pebbles, and rarely a minute 

 particle of shell : in one spot, the dermal armour and a 

 few bones of a Dasypoid quadruped were embedded in 

 it : it fills up furrows in the underlying gravel. With 

 the exception of the few pebbles and particles of shells, 

 this bed resembles the true Pampean mud ; but it still 

 more closely resembles the clayey flats (mentioned in 

 the eighth chapter) separating the successively rising 

 parallel ranges of sand-dunes. 



The bed (C) is of stratified gravel, like the lowest 

 one ; it fills up furrows in the underlying red mud, and 

 is sometimes interstratified with it, and sometimes in- 

 sensibly passes into it ; as the red mud thins out, this 

 upper gravel thickens. Shells are more numerous in 

 it than in the lower gravel ; but the bones, though 

 some are still present, are less numerous. In one part, 

 however, where this gravel and the red mud passed into 



