GEOLOGY OF PERU—ADAMS. 405 
by Raimondi to Gabb there was a collection from Payta. Gabb, 
in addition to describing them (1869), states that one set of four 
or five specimens was made up of extinct forms, while the remainder 
appeared to be Pliocene. 
Orton (1870) mentions some fossil shells of living species which 
he collected from the bluff at Payta and which were determined by 
Gabb. 
The portion of the Tertiary formations of the northern coastal 
plain lying between Payta and the Ecuadorian frontier was explored 
and described by Grzybowski (1899). He traveled from Payta to 
Talara, thence to Tumbez, and up the Tumbez River to Casadero, 
from which place he returned to the coast. He made the following 
divisions of the Tertiary: 
nOcenelee n= see Conglomerates 22 Payta formation. 
apneepNiecencue eae Shaleses 2 Rice ee Talara formation. 
SHIMON Zorritos formation. 
Lower Miocene____- Bituminous shales_______ -Heath formation. 
Oligocene__________ Hieroglyphic and massive 
Sand Stone aaa Ovibos formation. 
He collected and described fossils from these formations. The 
Oligocene, however, he distinguished more from stratigraphic rela- 
tions than by fossils. The paper is accompanied by a sketch map 
and sketch sections showing the localities where the formations were 
found. He observed a granite outcrop at Rica Playa, on the Tumbez 
River, and called certain rocks in the region of Casadero Paleozoic, 
but did not identify them by means of fossils. He regarded the Pale- 
ozoic as pushed up through the broken Tertiary. At Payta he noted 
a shale formation (no fossils) on which the Tertiary rests. 
Lacustrine Tertiary of the Sierra. 
In the Bolivian Plateau d’Orbigny (1842) described an ancient 
alluvial and pampean formation, the relations of which are shown 
in the section accompanying his report. Pissis (1856) also showed 
this formation but with an interbedded stratum of volcanic tuff in 
the Titicaca basin region. 
Forbes (1860) described the same deposits under the name “ De- 
luvial of the Interior” and explained that it varies from place to 
place according to the rocks from which it is derived. In his section 
he shows locally a bed of trachytic tuff and explained that it is seen 
in the valley of La Paz, in Bolivia. 
Agassiz (1876), in the paper accompanying his hydrographic 
sketch of Lake Titicaca, noted the lake deposits in the Titicaca basin 
and said that there are terraces up to 300-400 feet above the present 
level of the lake, and made some comments as to its former exten- 
