Maury — Porto Rican Tertiary Formation. 209 



Art. XVII. — On the Correlation of Porto Rican Tertiary 

 Formations with other Antillean and Mainland Hori- 

 zons-* by Carlotta Joaquina Maury. 



Review of Previous Work. 



Professor Charles P. Berkey in his ' i Geological Recon- 

 noissance of Porto Rico," 1 March 1915, differentiated 

 the formations of the island into the Younger Series 

 including the Tertiary to Recent, and the Older Series 

 constituting a very complex Pre-Tertiary group. It is 

 with the Younger Series only that this paper is con- 

 cerned. Provisionally, Dr. Berkey subdivided 2 the 

 Younger Series into: (1) the San Juan formation, com- 

 posed of Pleistocene sand dunes, and (2) the Arecibo 

 formation of limestones with associated shales and 

 marls. As phases of the Arecibo formation he men- 

 tioned the San Sebastian, or Lares shales, the Juana Diaz 

 marls and the Ponce chalk beds. Regarding the age Dr. 

 Berkey remarked: 3 "The Arecibo formation is of Ter- 

 tiary age. So far as identifications of the fossils have 

 gone, they appear to confirm the opinion that the larger 

 part of the formation belongs to the Oligocene epoch. 

 These determinations were based largely on collections 

 made in the heavy limestone beds and reefs in the vicinity 

 of the Quebradillas River. The shale beds lying at the 

 base of the series, and exposed farther to the south in the 

 vicinity of Lares, are certainly somewhat older and prob- 

 ably belong to the Eocene epoch. There are higher beds 

 developed rather irregularly that doubtless represent 

 still later time, referred by R. T. Hill to the Miocene 

 epoch, but these determinations must be left to future 

 detailed study of the formation as a whole." 



In June and July of 1915, Dr. Chester A. Reeds, 

 assisted by Mr. P. B. Hill, made a collection of inverte- 

 brate fossils from Porto Rico under the auspices of the 

 New York Academy of Sciences and the Porto Rican 

 Government, the American Museum of Natural History 

 cooperating. It is with the molluscs of this collection that 

 this summary report deals. Dr. Reeds, in a paper pre- 



* Published by permission of the Director of the American Museum of 

 Natural History. 



1 Ann. New York Acad. Sei., 26, pp. 1-70, PI. I-III, 1915. 



2 Op. cit., p. 10. 



3 Op. cit., p. 61. 



