Paleontology Zorritos Formation 3 



common to the two collections, indicates that the two col- 

 lectors probably worked in different localities. 



Grzybowski's account contained the sum total of data 

 available at the time \'an Hoist and Singewald began their 

 work. The complexity of the regional structure is too 

 great, and the sfratigraphic relationships are consequently 

 too deceiving to permit the obtaining of accurate results in 

 the short time spent at geologic observation by Grzybowski, 

 and it is not surprising to find that his deductions concerning 

 the Heath and Zorritos formations are frequently erroneous. 

 According to Singewald * the fossiliferous beds named as 

 Heath by Grzybowski are part of the \'ariegated formation, 

 the median member of the Zorritos formation, and the 

 correlation of its few fossils could not be clear with that 

 misconception as to its stratigraphic position in the way. 



Geology of the Zorritos District. 



The coastal region of northern Peru is desert from the 

 Gulf of Guayaquil southward to the Morrope valley, a dis- 

 tance of about 200 miles. The coast is fronted as a rule by 

 barren cliffs which are broken here and there by quebradas, 

 or narrow valleys, which extend inland : where sandstone 

 is the underlying rock the cliffs are prominent, and where 

 shales occur there are no cliffs. The region behind the 

 cliffs is of bare hills, which extend in continuous succession 

 from the coast to the Cordillera d'Amotape. a coast range 

 about 2000 feet in average height, about 35 miles from 

 the Pacific Ocean in the latitude of Zorritos. and much 

 nearer to the coast in the vicinity of Negritos. In the 

 vicinity of Payta the country inland is more or less even, 

 consisting of a sandy plateau, but to the north of Cabo 

 Blanco it is rough, and sharp hills and narrow quebradas 

 break the surface into an irregular, inaccessible region. 

 The rainfall is practically nothing, and the only signs of 



* Singewald. J. T.. Jr., personal communication. 



