STRATIGRAPHIC SIGNIFICANCE OF THE SPECIES. 117 



Jique de la Ar gotta: Three species of echinoids collected at this 

 locality indicate a deposit of Oligocene age, but the evidence is in- 

 sufficient to decide what horizon is represented. 



Monte Toro: The single species, Clypeaster cotteaui Egozcue, found 

 at this locality indicates Antiguan Oligocene. 



TERTIARY ECHINOIDS FROM PORTO RICO. 



The discussion of the Porto Rican echinoids will be introduced by 

 quoting Dr. Carlotta J. Maury's table of geological formations in 

 Porto Rico. 1 Dr. Maury correlated the middle Oligocene of her table 

 with the Antigua formation and the upper Oligocene of her table 

 with the Anguilla formation. 



Table of Tertiary formations in Porto Rico {after C. J. Maury). 



On the following page is a table of the Tertiary echinoids from Porto 

 Rico described by Doctor Jackson in his paper. 



First, with regard to the "Arecibo" formation of Berkey, according 

 to Berkey's original description of the formation, 2 it seems to me that 

 he intended the name to apply to all deposits between the Cretaceous 

 and Pleistocene in Porto Rico, and that he included in it the San 

 Sebastian, Lares, and Collazo shales. 



According to the information supplied Doctor Jackson on horizons 

 whence the echinoids came, the base of the "Arecibo" formation, 

 the Collazo shale, and the San Sebastian shale represent one horizon. 

 This horizon has Echinolampas lycopersicus in common with the 



i Maury, C. J., Tertiary Mollusca from Porto Rico: New York Acad. Sci. Scientific Survey of 

 Porto Rico and the Virgin Islands, vol. 3, part 1, table opposite p. 4, 1920. 



2 Berkey, Charles P., Geological Reconnaissance of Porto Rico, New York Acad. Sci. Ann., 

 vol. 26, pp. 12-17, 1915. 



