Chapter XX: Appendix: B

FOSSIL DETERMINATIONS

A few fossil collections were gathered in order that age determinations might be made. With the following identifications I have included a few fossils (I and II) collected by W. R. Rumbold and put into my hands in 1907. The Silurian is from a Bolivian locality south of La Paz but in the great belt of shales, slates, and schists which forms one of the oldest sedimentary series in the Eastern Andes of Peru as well as Bolivia. While no fossils were found in this series in Peru the rocks are provisionally referred to the Silurian. Fossil-bearing Carboniferous overlies them but no other indication of their age was obtained save their general position in the belt of schists already mentioned. I am indebted to Professor Charles Schuchert of Yale University for the following determinations.

I. _Silurian_

San Roque Mine, southwest slope of Santa Vela Cruz, Canton Ichocu, Province
Inquisivi, Bolivia.

Sent by William R. Rumbold in 1907.

_Climacograptus?_
_Pholidops trombetana_ Clarke?
_Chonetes striatellus_ (Dalman).
_Atrypa marginalis_ (Dalman)?
_Cœlospira_ n. sp.
_Ctenodonta_, 2 or more species.
_Hyolithes._
_Klœdenia._
_Calymene?_
_Dalmanites_, a large species with a terminal tail spine.
_Acidaspis._

These fossils indicate unmistakably Silurian and probably Middle Silurian. As all are from blue-black shales, brachiopods are the rarer fossils, while bivalves and trilobites are the common forms. The faunal aspect does not suggest relationship with that of Brazil as described by J. M. Clarke and not at all with that of North America. I believe this is the first time that Silurian fossils have been discovered in the high Andes.

II. LOWER DEVONIAN

Near north end of Lake Titicaca.

_Leptocœlia flabellites_ (Conrad), very common.
_Atrypa reticularis_ (Linnæus)?

This is a part of the well-known and widely distributed Lower Devonian fauna of the southern hemisphere.

III. _Upper Carboniferous_

All of the Upper Carboniferous lots of fossils represent the well-known South American fauna first noted by d’Orbigny in 1842, and later added to by Orville Derby. The time represented is the equivalent of the Pennsylvanian of North America.

Huascatay between Pasaje and Huancarama.

Crinoidal limestone.
Trepostomata Bryozoa.
_Polypora._ Common.
_Streptorhynchus hallianus_ Derby. Common.
_Chonetes glaber_ Geinitz. Rare.
_Productus humboldti_ d’Orb. Rare.
" _cora_ d’Orb. Rare.
" _chandlessii_ Derby.
" sp. undet. Common.
" sp. undet. "
_Spirifer condor_ d’Orb. Common.
_Hustedia mormoni_ (Marcou). Rare.
_Seminula argentea_ (Shepard). "

Pampaconas, Pampaconas valley near Vilcabamba.

_Lophophyllum?_
_Rhombopora_, etc.
_Productus._
_Camarophoria._ Common.
_Spirifer condor_ d’Orb.
_Hustedia mormoni_ (Marcou).
_Euomphalus._ Large form.

Pongo de Mainique. Extreme eastern edge of Peruvian Cordillera.

_Lophophyllum._
_Productus chandlessii_ Derby.
" _cora_ d’Orb.
_Orthotetes correanus_ (Derby).
_Spirifer condor_ d’Orb.

River bowlders and stones of Urubamba river, just beyond eastern edge of
Cordillera at mouth of Ticumpinea river. (Detached and transported by stream
action from the Upper Carboniferous at Pongo de Mainique.)

Mostly Trepostomata Bryozoa.
Many _Productus_ spines.
_Productus cora_ d’Orb.
_Camarophoria_. Same as at Pampaconas.
_Productus_ sp. undet.

Cotahuasi A.

_Lophophyllum._
_Productus peruvianus_ d’Orb.
" sp. undet.
_Camarophoria._
_Pugnax_ near _utah_ (Marcou).
_Seminula argentea_ (Shepard)?

Cotahuasi B.

_Productus cora_ d’Orb.
" near _semireticulatus_ (Martin).

IV. _Comanchian or Lower Cretaceous_

Near Chuquibambilla.

_Pecten_ near _quadricostatus_ Sowerby.
Undet. bivalves and gastropods.
The echinid _Laganum? colombianum_ d’Orb. A clypeasterid.

This Lower Cretaceous locality is evidently of the same horizon as that of Colombia illustrated by d’Orbigny in 1842 and described on pages 63-105.