THE PALEONTOLOGY OF THE ZORRITOS 



FORMATION OF THE NORTH PERUVIAN 



OIL FIELDS.* 



INTRODUCTION. 



This paper presents the results of a detailed study of a 

 collection of mollusks made by Dr. Joseph T. Singewald, Jr., 

 from the Zorritos formation of northern Peru. Much of the 

 value their evidence offers is due to the careful stratigraphic 

 work done by Dr. van Hoist, of the Hague, Holland, and 

 Dr. Singewald, as a result of which the position of the 

 subsidiary units of the Zorritos formation has been estab- 

 lished, and a number of misconceptions concerning the 

 relationships of the units to themselves and to the under- 

 lying Heath formation have. been corrected. 1 



PREVIOUS WORK. 



The first account of fossils from the neighborhood of 

 Zorritos was published in 1870 by Edward T. Nelson 2 as a 

 graduating thesis in the Sheffield Scientific School of Yale 

 Universitv. This work was based on a collection of fossils 



* George Huntington Williams Memorial Publication No. 14. 



1 The author wishes to express his indebtedness to Professor 

 Edward W. Berry under whose direction the work was done, 

 and to Dr. J. T. Singewald, Jr., of the Johns Hopkins University; 

 to Messrs. W. H. Dall, T. Wayland Vaughan, W. P. Woodring, 

 and Miss Julia A. Gardner of the U. S. Geological Survey and 

 U. S. National Museum ; and to Professor Charles Schuchert of 

 the Peabody Museum, and Dr. Henry A. Pilsbry of the Philadel- 

 phia Academy for the loan of material. The figures are the work 

 of George S. Barkentin. 



2 On the Molluscan Fauna of the Later Tertiary of Peru, Trans. 

 Conn. Acad., vol. 2, pp. 186-206, 1870. 



