GEOLOGY OF PERU—ADAMS. 399 
Carboniferous or Permian. It will be remembered that d’Orbigny 
described Chemnitzia potosensis from the Triassic, but the diagnostic 
value of the genus for indicating the Carboniferous or Permian may 
well be questioned, since the genus is also found in the Mesozoic. 
Moreover, it will be recalled that the evidence by Steinmann just cited 
is Popaced to the conclusions of Dereims. 
TRIASSIC. 
D’Orbigny (1842) referred to the Triassic a series of variegated 
reddish sandstones in Bolivia. He found a number of fossils but 
mentions only one, Chemnitzia potosensis, the others having been lost. 
The age of these beds seems to still be in doubt, Dereims having re- 
ferred them (1906) to the permo-Carboniferous as has already been 
mentioned. 
Later Forbes (1861) commented on the classification by d’Orbigny 
and states that it would appear that d’Orbigny proceeded on the 
supposition that no link in the geologic chain should be deficient. 
Forbes classed these rocks as Permian or Jurassic, but stated that 
their age is a question requiring more study. 
Raimondi (1873) in his volume on the Department of Ancachs 
classed as Triassic certain red sandstones and shales with salt and 
gypsum. ‘This seems to have been done in accordance with the gen- 
eral relations of the rocks and to make the geologic succession com- 
plete. It will be remembered that the fossils sent by Raimondi to 
Gabb were not given close diagnostic values, and so the classification 
by Raimondi has really little value. In several places Raimondi 
speaks of the Triassic as being present, but unfortunately little reli- 
ance can be placed on this. According to Steinmann’s later writings 
(1904) the red sandstones and shales with salt and gypsum beds are 
to be classed as Cretaceous (Lower Liassic) .” 
JURASSIC. 
D’Orbigny (1842) found no fossils of Jurassic age and did not 
color any part of his section as Jurassic. He discussed the prob- 
abilities of its being present in South America. 
Crosnier (1852), in his explorations on the east slope of the Cor- 
dillera Occidental, found some fossils which were determined by M. 
Bayle as Jurassic. He mentions an Arca like Arca gabnelis of the 
Neocomian. Also an Ammonite from near Oroya was likewise de- 
termined as Jurassic. 
Forbes (1860) classed as Jurassic or Permian a series consisting 
principally of sandstones aggregating more than 6,000 feet. These 
“Bol. No. 12, p. 24. 
