200 Elevation of Patagonia. paet n. 



plains have very level surfaces ; but all are scooped out 

 by numerous, broad, winding, flat-bottomed valleys, in 

 which, judging from the bushes, streams never flow. 

 These remarks on the state of the shells, and on the 

 nature of the plains, apply to the following cases, so 

 need not be repeated. 



Southward of Port Desire, the plains have been 

 greatly denuded, with only small pieces of table-land 

 marking their former extension. But opposite Bird Is- 

 land, two considerable step-formed plains were measured, 

 and found respectively to be 350 and 590 feet in height. 

 This latter plain extends along the coast close to Port 

 St. Julian (110 miles south of Port Desire) ; where we 

 have the following section : — 



£ 





No. 18. 













Section of Plains at Port St. Julian. 











950 ft. An. 3JL 









a . 







\ 560 An. M. 



\_ 430 An. M. 



" \ 



00 



o 



o o 

 m a 





\ 



\ 



Level of sea. Scale -^ of inch to 100 feet vertical 



The lowest plain was estimated at ninety feet : it is 

 remarkable from the usual gravel-bed being deeply 

 worn into hollows, which are filled up with, as well as 

 the general surface covered by, sandy and reddish earthy 

 matter : in one of the hollows thus filled up, the skeleton 

 of the Macrauchenia Patachonica, as will hereafter be 

 described, was embedded. On the surface and in the 

 upper parts of this earthy mass, there were numerous 

 shells of Mytilus Magellanicus and M. eduUs, Patella 

 deaarita, and fragments of other species. This plain 

 is tolerably level, but not extensive ; it forms a pro- 

 montory seven or eight miles long, and three or four 

 wide. The upper plains in the above diagram were 



