66 THE NEOG^IC REALM. [CHAP. 



At the present day the mammalian fauna of Neogaea is mark- 

 edly distinct not only from that of Notogaea but likewise from that 

 of the whole of the rest of the globe (Arctogsea), although the dis- 

 tinction is now, owing to free communication with the north, 

 much less marked than it was in Tertiary times, and it is accord- 

 ingly essential to enter at once into the consideration of the 

 extinct forms in order to show why this part of the world is 

 entitled to rank as one of three primary zoological regions. 



There are several districts in South America where fossil 

 Mammal- remains of mammals have been found ; most of these 

 iferous being remarkable for the extraordinary profusion in 



which the bones occur. The first that may be men- 

 tioned are the celebrated caves of Lagoa Santa, in the province of 

 Minas Geraes, to the northward of Rio, which have yielded re- 

 mains of a great variety of Plistocene genera and species, inclusive 

 of those of man. Probably contemporaneous with these are the 

 sand-dunes on the coast of Buenos Aires, which likewise contain 

 human remains in association with those of extinct mammals ; 

 while the so-called Pampean beds of the Argentine pampas are 

 apparently somewhat older, although still pertaining to the Plisto- 

 cene period. As these Pampean deposits are exceedingly rich in 

 fossil mammals, they may be described in some detail. They 

 form the great level tract of country extending southwards from 

 the Rio de la Plata and the Parana to the Rio Colorado, south of 

 Bahia Blanca, and westwards from the Atlantic seaboard about 

 half the distance to the Andes; thus occupying some 200,000 

 square miles of country. The pampas is an almost level grass- 

 covered plain, intersected by water-courses, and penetrated near 

 its margins by small mountain-ranges, while it is almost entirely 

 barren of trees. It is composed of a- rich black alluvial mud, 

 mingled with beds of sand, and underlain by, or in some places 

 interstratified with layers of a hard white calcareous deposit 

 known as tosca\ but in certain spots it contains beds of marine 

 shells belonging to species still living in the adjacent seas. Except 

 in those spots where the tosca comes to the surface, there is not a 

 stone or a pebble to be seen in the whole deposit, and near 

 Buenos Aires the formation has been bored to a depth of ninety 

 feet without touching bottom. From its composition it is evident 



