80 BULLETIN'- MUSEUM OF COMPARATIVE ZOOLOGY. 



actually attaining that of spherical sepai'ation, thus producing the 

 bales shown in the Rio Negro section, characteristic of many weather- 

 ing basalts, an effect coupled with the want of definite stratification 

 within the stratum. 



Once the tillite beds imderlying sandstones are reached by dissecting 

 streams or rivers, the overlying strata widen out with steep cliffs, the 

 small streams falling over these rocks have falls, and, owing to the 

 ready removal of the tillite and the growth of the main valley in this 

 section, the side streams present the appearance of hung up valleys. 



Age of the Bouldcr-Brds. — As commonly stated on the authority of 

 Dr. Derby the boulder-bearing deposits are to be regarded as the 

 equivalent of the Upper Carbonic or Permian glacial period now 

 recognized in India, Australia, ahd South Africa. This Permian age 

 of the beds in Brazil was accepted by Professor Pranner in his Geologia 

 elementar (Rio de Janeiro and Sao Paulo, 190G), and still more 

 recently by Dr. I. C. White in his Report on the Brazilian coal field. 

 In the same monograph, Mr. David \Yhite presents the most complete 

 description and analysis of the flora of the south Brazilian field yet 

 published. From this report it appears that the flora succeeding the 

 conglomerates on the south in Santa Catharina are of the Lower 

 Gondwana type which immediately succeeds the glacial beds in India 

 and elsewhere in the eastern hemisphere. Dr. David White corre- 

 lates the Jaguaricatu beds [Orleans conglomerate] and associated 

 sandstones and shales of Dr. I. C. White with the Talchir beds of 

 India, the Dwyka conglomerate of South Africa, and the basal 

 conglomerate of the Permian series of Argentina. 



Divisibility of the Glacial Beds. — The question is naturally asked 

 whether there was one or more than one episode of glaciation or ice- 

 action in southern Brazil. The facts concerning the distribution of 

 conglomerates in this field are as yet too little known to enable one to 

 give a satisfactory statement in reply to such a question. The 

 localization of the typical tillite beds near the base of the series so 

 suggestive of local contributions of debris complicates the question. 

 If the conglomerate beneath the whitish sandstone at Serrinha Station 

 with its glaciated fragment be of Permian age and pass, as it appears to, 

 beneath the boulder-bearing beds exposed westward and southwards 

 towards Lapa, then in that section there are evidences of two epochs 

 of ice-action separated by the deposition of the sandstone beds which 

 form the walls of the gorge of the Iguassii. 



The tendency of the boulders to display themselves in a marked 

 jnanner in certain zones often only a few feet apart is evidently a 



