398 TUE CRETACEOUS AND TERTlAKY GEOLOGY 



fossils occur, for the most part, lying loose in the road where they have constantly 

 been ridden and walked over, or are imbedded in the black residuary earth that 

 covers these cretaceous hills. In many cases, however, there are irregular blocks of 

 the matrix preserved along with the fossils. The worn appearance of a great many of 

 the specimens from this locality is due to two causes : one is the rapid dissolving 

 action of the rain-water, which when raised to a high temperature by falling upon the 

 hot rocks, attacks them vigorously and leaves an etched surface such as is produced 

 by acid acting upon a calcareous sandstone ; the second is the wearing of the rocks 

 against each other where they are constantly walked and ridden over in the road. 

 There is nothing in the rocks themselves, in their topographic position, or in their rela- 

 tions to the underlying strata to lead one to suppose that these fossils have been carried 

 here from a lower geologic horizon. 



Attention is called to the relation of the Bom Jesus beds to those of Larangeiras 

 and Pedra Furada, and to the fact that the Larangeiras beds are the equivalents of 

 those of Lastro, etc., at Maroim, and of those of Urubti on the Rio Sergipe. 



At Maroim the Lastro beds are overlain by a similar cephalopod-bearing forma- 

 tion, that of Garajau, which yields other fossils of Jurassic aspect, while those of 

 Urubii, the equivalents of the Lastro beds, overlie others of decidedly Jurassic facies. 



We have then the following arrangement of the strata : 



1. At the top are the Garajau and Bom Jesus beds, yielding fossils of both creta- 

 ceous and Jurassic aspect. 



2. Beneath these arc the Lastro, Jaque, LTrubu, Imbira, Toque, Capoeira, Larangei- 

 ras, and Pedra Furada beds, whose fossils are all referable to the cretaceous. 



3. Beneath these are the beds of Porto dos Barcos, Trapiche Maior, Trapiche das 

 Pedras Novo, Trapiche das Pedras Velho, and Coqueiro, all of which yield fossils of 

 both cretaceous and Jurassic aspects. 



As the Jurassic aspect of both the underlying and the overlying beds might tend 

 to throw doubt upon the reference of those of Urubii, Lastro, etc., to the cretaceous, 

 I can only refer to Dr. White's able discussion of this subject in his " Contributions " 

 (pp. 15-10), where he shows that the weight of evidence favors the cretaceous age, 

 not only of those particular beds, but of the entire Sergipe- Alagoas series. 



It is no longer cause for surprise that beds of decided Jurassic aspects are found 

 overlying others of just as marked cretaceous aspect. Dr. Blanford, in his presiden- 

 tial address before the Geological Section of the British Association at Montreal in 1885, 

 laid timely stress upon these apparently anomalous conditions existing in India and 

 South Africa, and to tlie grave difficulty or impossibility of an exact and minute 



