VALLEY OF THE AMAZONS. 
195 
senting the Jura range. As if to complete 
the comparison, I found Alpine lichens grow¬ 
ing among cactus and palms, and a crust of 
Arctic cryptogamous growth covered rocks 
between which sprang tropical flowers. On 
the northern flank of this serra I found the 
only genuine erratic boulders I have seen in 
the wdiole length of the Amazonian Valley, 
from Para to the frontier of Peru, though 
there are many detached masses of rock, as, 
for instance, at Pedreira, near the junction of 
the Rio Negro and Rio Branco, which might 
be mistaken for them, but are due to the 
decomposition of the rocks in place. The 
boulders of Errerd are entirely distinct from 
the rock of the serra, and consist of masses of 
compact hornblende. 
It would seem that these two ranges skirt¬ 
ing a part of the northern and southern banks 
of the Lower Amazons are not the only rem¬ 
nants of this arenaceous formation in its prim¬ 
itive altitude. On the banks of the Japura, in 
the serra of Cupati, Major Coutinho has found 
the same beds rising to the same height. It 
thus appears, by positive evidence, that over an 
extent of a thousand miles these deposits had 
