OF THE SERGIPE-ALAGUAS BASIN OF BRAZIL. 395 



supposing that they have been redeposited, as I shall show hereafter, and the case is 

 mentioned in this place only to call attention to what is either contlicting testimony 

 regarding the age of the SeYgipe rocks, or to a mingling in them of Jurassic and creta- 

 c9om faunas. 



M. Emmanuel Liais, in speaking of the secondary deposits of Brazil, in his " Geol- 

 ogic du Bresil " (p. 197) says: "Ce puissant depot secondaire, tout parait I'indiquer 

 d'ailleurs, a dii se former pendant au moins une grande partie de Tepoque cretacee, et a 

 pent etre commence dcs Tcpoque jurassique, au moins dcs la periode oolithique. Pen de 

 perturbations auront eu lieu dans ces immenses regions pendant cette longue duree, et 

 par la s'explique comment les especes du commencement de la periode ont pu continuer 

 d'exister et se meler aux especes posterieures, de sorte que, suivant la tros judicieuse 

 remarque de Darwin, confirmee, comme nous I'avons vu, par I'union d'especes jurassiques 

 et cietacees dans les divers depots du Bresil, les deux epoques ne sent pas nettement 

 separees comme en Europe." 



No direct reference, however, is here made to the mesozoic geology of the Sergipe- 

 Alagoas basin. The writer has not been able to locate this opinion of Mr. Darwin, and 

 does not know upon what evidence it is based, but from the limits of his (Darwin's) ob- 

 servations in Northeastern Brazil, it is presumed that such an opinion by Mr. Darwin 

 must necessarily have been based upon evidence accumulated by him in the Argentine 

 Republic and Patagonia. 



In his "Contributions" Dr. White gives the following reasons for calling the rocks 

 of the Sergipe-Alagoas region cretaceous (p. 15) : "First, the majority of the types are 

 such as are generally regarded as characteristic of that period. Second, a portion of the 

 species are identified with published species of undisputed cretaceous fossils in other 

 parts of the world. Third, although some of the species have a Jurassic aspect, none of 

 them arc identifiable with any known Jurassic species. Finally, as all the collections 

 have been shown to belong to one liiuna, and a part of its species to be certainly of cre- 

 taceous age, the whole fauna must necefisarily be referred to that period." This decision 

 is somewhat weakened, however, by a statement (on p. 6) to the effect that " while 

 such a conclusion would, I think, have been reasonably reached from a study of 

 the fossils alone, much reliance has been placed in the corroborative testimony of the 

 geologists of the Brazilian Survey." 



If the members of the former Brazilian survey were now asked to give tlit-ir 

 reasons for calling these rocks cretaceous, they would lay all stress upon Dr. White s 

 determinations and none at all, or very little, upon any evidence that has been 

 adduced from stratigraphic relations, simply because, as has already been said, those 



