26 BULLETIX: MUSEU:VI OF COMPARATIVE ZOOLOGY. 



broken into by some burrowing animal and many colonies were aban- 

 doned. This cycle of change must several times have worked over the 

 surface materials of the campos of Brazil and facilitated the work of 

 erosion by winds and rain. 



When it is recalled that a large insectivorous fauna including the 

 anteaters, Myrmecophagidae (Vermilinguia), inhabit the ant-occupied 

 surface of Brazil and that this group is specialized with reference to 

 the ants and that traces of this organic adaptation go back to Pliocene 

 times, it is evident that ants and anteaters have exercised an important 

 function in the geologic processes which have worked together in the 

 evolution of the surface deposits of Brazil. Fossil ants are numerous 

 in the Oligocene beds of Florissant in Colorado (Scudder) and ant- 

 eaters appear in the Miocene Santa Cruz formation of South America, 

 dates which are as far back if not earlier than the beginnings of the 

 present surface deposits of the Brazilian highlands. 



August 29ih. — The road northward from the camp at the dike 

 passed over alternating beds of red shale and yellowish to reddish 

 sandstones, dipping gently- to the northwest towards the southern 

 margin of the trap sheets, whose escarpment, as far as it could be seen, 

 extended in a northeast-southwest direction roughly parallel to the 

 strike of the underlying sediments. From the top of one of the 

 monoclinal ridges between the Rio Ponte alto and the Rio Canoas, this 

 escarpment could be traced to the eastern horizon where a conical 

 outlier stood out in clear relief as a monument to the erosion of the 

 trap co\-er which formerly extender! o\-er the Lages area. 



Fio. 1. — Field sketch of the trap plateau northwest from Kio Marombas iu 

 Santa Catharina. 



The monoclinal structure of the sediments results in a series of ridges 

 with steeper faces on the southeast and longer gentle slopes to the 

 northwest. At about twelve kilometers from camp we crossed the 

 Canoas River, and continued northward to the north bank of the Rio 

 Ponte alto where we camped by a covered bridge. The stream at this 

 point flows in a channel about twenty feet deep over sandstones with 

 an active drainage. 



August 30th. — After a march of an hour and fifty minutes from 

 camp we passed over sandstones striking northwest and dipping about 

 15 degrees to the northeast. About forty-five minutes later we 



