176 Papers from the Marine Biological Laboratory at Tortugas. 



hamas, eastern side, below the lighthouse. This is probably an aeolian 

 sandstone, and exhibits cross-bedding very well. Plate 7, fig. b, repre- 

 sents the western beach of Loggerhead Key, Tortugas, looking northeast. 

 It shows indurated calcareous sandstone along the water's edge and 

 loose calcareous sands higher on the beach slope. Note the continuity 

 of the slope of the lower indurated with that of the higher unconsolidated 

 material. 



The material represented in all of the illustrations mentioned is of 

 detrital origin, and illustrates bedding by shore waves and the wind. 

 Plate 14, fig. a, illustrates cross-bedding in a water-laid deposit. 



Plate 13, fig. b, represents exposures of the Miami oolite. The sharp 

 cross-bedding is brought out, but the rock occurs in distinct ledges. 

 This massive bedding with the cross-bedding of the smaller divisions is 

 suggestive, and it should be emphasized that the oolite granules are 

 not similar to the detrital sands composing the Bahaman and Tortugas 

 exposures. 



The data so far presented indicate an individuality of the Floridian 

 oolite areas diflferent from that of the other areas discussed, although as 

 yet definite criteria for determining the conditions under which the oolite 

 was formed have not been advanced. Cross-bedding may be due to 

 current, wave, or wind action, and the three processes may be more or 

 less cooperative. 



Illustrations of the surfaces of two oolitic keys bear on the solution 

 of the problem, viz: Plate 14, fig. c, which represents Summerland Key; 

 and plate 15, fig. a, a view of Boca Grande Key, show remarkably flat 

 surfaces, not in the least suggestive of dunes. On Big Pine Key the 

 surface of the oolite shows mud cracks from drying (plate 14, fig. b). 

 Fortunately the oolites are rather rich in fossils. 



Fossils from the Miami Oolite} 

 Locality: Golf Ground, Miami. 



Cyphastrea hyades (Dana). Glycymeris pectinata Gmelin. 



Conus floridanus Gabb. Avicula atlantica Lara. 



Columbella mercatoria Lam. Laevicardium serratum Linn. 



Cerithium muscarum Say. Codakia orbicularis Lam. 



littoratum Born. Phacoides pennsylvanicus Linn. 



Area gradata Broderip. Chione cancellata Linn. 



Locality: Kronkheit-Offer Quarry, Miami.' 



Siderastrea radians (Pallas) . Livona pica Linn. 



Strombus gigas Linn. 



Correlation. — The species are all Recent, and the age of the oolite 

 is therefore Pleistocene. 



Locality: Buena Vista.' 

 Mellita sexforis Lamarck. 



Fossils from tlie Key West Oolite. 

 Locality: Big Pine Key (collected by Samuel Sanford). 

 Mussa (Isophyllia) sp. Cardium isocardia Linn. 



Encope michelini Agassiz. Lasvicardium serratum Linn. 



Terebra dislocata Say. Phacoides pennsylvanicus Linn. 



Strombus pugilis Linn Divaricella densata Wood. 



'The fossils from these localities were presented by Dr. J. N. McGonigle, of Miami. 



