EVIDENCES OF MARINE ORIGIN. 61 



upheaval of the whole seaboard country by some geological 

 agency, and the elevation of the coast above the level of the 

 ocean. When the sand-hills and the submarine lagoons were 

 raised, the basins contained sea or salt water, and must have 

 been so many small salt lakes along the sea-coast, having their 

 bottoms covered or paved with a thin layer of the nodular 

 fragments of marl rock. As the evaporation of the salt water 

 progressed, what was left became, day after day, a stronger 

 brine, until at last a deposit of salt ultimately formed as a 

 crust upon the pavement of marl rock." It is easy to under- 

 stand that there must have been vast numbers of these basins, 

 extending over a vast area, lying at irregular intervals, and 

 as irregular in shape as the ponds and lakes scattered over 

 the face of the country at the present time. 



It is a curious fact, and affords striking confirmation of 

 this theory of the origin of these nodules, that they are com- 

 posed, like the mother-rock from which we have seen that 

 they were broken off, of the dead shells of marine animals. 

 So far as the mechanical structure of these specimens of the 

 phosphate rocks is concerned, it is wonderfully similar to that 

 of the marl-bed, and nearly every sample is filled, not merely 

 with the broken fragments of marine shells and coral animals, 

 but with innumerable perfect casts of fossilized shells, perfectly 

 apparent to the naked eye. The nodules also, like the mother- 

 bed of eocene marl, contain the teeth and bones of sharks, 

 whale-like and alligator-like animals, such as lived in the sea, 

 absolutely inclosed and imbedded in them, but no remains of 

 land animals are so inclosed and imbedded in the nodules 

 found in these phosphate basins. The remains of laud ani- 

 mals are found in great quantities, mingled with but not shut 

 or inclosed in the nodules, showing that they found their Avay 

 among: them after the elevation of the basins above the ocean 

 level. 



I have already alluded to the great number of species of 

 gigantic quadrupeds, now wholly extinct, that are known to 

 have existed and abounded in those regions, and Prof. Holmes 

 supposes that these terrestrial monsters "repaired periodically 

 to these salt lakes or lagoons, or, as they are called in Ken- 

 tucky, 'salt-licks,' and, during a series of indefinite ages, 

 engaged as they were, first sipping brine, then licking salt, 



