GEOLOGY OF PERU ADAMS. 401 



D'Orbigny discussed the occurrence of the Cretaceous in South 

 America, and in his section shows an extension of porphyritic rocks 

 on the west slope of the Cordillera Occidental; he did not differ- 

 entiate the Cretaceous, but evidently included them with the por- 

 phyries w^ith which they are interbedded. 



In the section which Forbes made from Arica to Bolivia he classi- 

 fied (1861) as oolitic (Liassic) the rocks at Arica, which he describes 

 as shales, claystones, and embedded porphyries, and stated as his rea- 

 son for doing so that to the south of the district which he studied 

 the rocks are abundantly fossiliferous and had yielded to the re- 

 searches of Bayle and Coquand and Phillipi about 35 species of 

 recognized oolitic forms. On his map he showed a considerable ex- 

 tent of oolitic in the Cordillera Occidental of southern Peru. 



Apparently, Raimondi attempted to identify the fossils which he 

 collected, although he did not describe them. He evidently used the 

 fossils as a guide in determining as best he could the age of the sedi- 

 mentary formation, which he discusses in his various writings. When 

 h^ sent his collections to Gabb to be described he accompanied them 

 by a letter (1867) in which he outlined the geographical distribution 

 of the sedimentary formations of Peru. According to his idea, 

 Cretaceous (with Jurassic, Lias, and Trias) is distributed principally 

 in the western Cordillera. He thought the stratified rocks near the 

 Port of Ancon, at San Lorenzo, near Callao, and at Chorillos, to be 

 Jurassic or Liassic. These localities have since proven to be Creta- 

 ceous, as will soon appear in this paper. Unfortunately, Gabb's de- 

 termination of the Mesozoic fossils was delayed and, moreover, he 

 did not give to them such diagnostic value as would help Raimondi to 

 revise his ideas in his later writings. 



In his volume on the Department of Ancachs he classed (1873) as 

 Cretaceous certain limestones with echinoderms, oysters, and other 

 fossils. This seems to be correct as viewed in connection with the 

 determination of the Cretaceous in other localities, where it con- 

 sists largely of limestone and contains similar fossils. 



In his geological sketches (1876) Agassiz states that Mr. William 

 Chandless, upon his return from the River Purus, presented him 

 with fossil remains of the highest interest and undoubtedly belong- 

 ing to the Cretaceous. They were collected on the River Aquiry, 

 latitude 10°-11° south, longitude 67°-69° west, in localities varying 

 from 430 to 650 feet above sea level. Among the material, remains 

 of a Morosaurus and of fishes were found. Chandless <^ says that the 

 material identified by Agassiz consisted of two perfectly preserved 

 vertebrae of Morosaurus. These are the only vertebrate remains thus 



<» " Notes on the River Aquiry, the principal affluent of the Purus," William 

 Chandless, Journal Royal Geogr. Soc, Vol. 36, p. 119. 



