Contents, xi 



tion of valleys — Boulders moved by earthquake -waves — Saline 

 superficial deposits — Bed of nitrate of soda at Iquique — Saline 

 incrustations — Salt-lakes of La Plata and Patagonia ; purity of 

 the salt ; its origin ,..,.. page 283 



CHAPTER XL 



ON THE FOEMATIONS OF THE PAMPAS. 



Mineralogical constitution — Microscopical structure — Buenos Ayres, 

 shells embedded in tosca-rock — Buenos Ayres to the Colorado — 

 S. Ventana — Bahia Blanca; M. Hermoso, bones and infusoria of; 

 P. Alta, shells, bones, and infusoria of ; co-existence of the recent 

 shells and extinct mammifers — Buenos Ayres to St. Fe — 

 Skeletons of Mastodon — Infusoria — Inferior marine tertiary 

 strata, their age — Horse's tooth. Banda Oeiental — Superficial 

 Pampean formation — Inferior tertiary strata, variation of, con- 

 nected with volcanic action ; Macruchenia Patachonica at S. 

 Julian in Patagonia, age of, subsequent to living mollusca and to 

 the erratic block period. Summaey — Area of Pampean forma- 

 tion — Theories of origin — Source of sediment — Estuary origin — 

 Contemporaneous with existing mollusca — Relations to under- 

 lying tertiary strata — Ancient deposit of estuary origin— Eleva- 

 tion and successive deposition of the Pampean formation — 

 Number and state of the remains of mammifers ; their habitation, 

 food, extinction, and range — Conclusion — Supplement on the 

 thickness of the Pampean Formation — Localities in Pampas at 

 which mammiferous remains have been found . . 313 



CHAPTER XII. 



ON THE OLDER TEETIAET FORMATIONS OF PATAGONIA AND CHILE. 



Bio Negro— S. Josef — Port Desire, white pumiceous mudstone with 

 infusoria — Port S. Julian — Santa Cruz, basaltic lava of — P. 

 Gallegos — Eastern Tierra del Fuego ; leaves of extinct beech 

 trees — Summary on the Patagonian tertiary formations — Tertiary 

 formations of the Western Coast — Chonos and Chiloe groups, 

 volcanic rocks of — Concepcion — Navidad — Coquimbo — Summary 

 — Age of the tertiary formations — Lines of elevation — Silicified 

 wood — Comparative ranges of the extinct and living Mollusca on 

 the West Coast of S. America — Climate of the tertiarj 7 period — 

 On the causes of the absence of recent conchiferous deposits on 

 the coasts of S. America — On the contemporaneous deposition 

 and preservation of sedimentary formations . . . 370 



