130 PROCEEDmGS OF THE [Dec, 1886. 



ing from the size of a potato to several feet in diameter. The other or river 

 rock is generally found in a layer or sheet of tightly compacted nodules, over- 

 l3dng the marl at the bottom of rivers and creeks, where it either forms the 

 bottom itself, or is overlaid by a deposit of mud of greater or less depth. 



The difference between the compacted mass of river rock and the detached 

 nodules of land rock can be accounted for by remembering that the coast belt 

 of South Carolina, inside of the sea islands, and for some distance in the interi- 

 or, has been formed by alluvial deposits on the banks of the rivers, with sandy 

 spaces between, which have been accumulated by the action of the ocean, and 

 overljdng in most places a stratum of claj" of varying depth and thickness. In 

 these sandy spaces the nodules are mined, and, besides being in many cases 

 evidently waterworn, the manner in which they lie is proof that they have 

 been subjected to the operation of waves and currents, previous to having been 

 covered by the accretions from the ocean. Thus their origin is probably the 

 same as the river rock, from which they became broken off and moved to a 

 short distance inland. 



There are interspersed among the nodules of land rock, the mammalian 

 bones of the mastodon, elephant, bison, tapu-, deer, fossil horse and domestic 

 cow and hog, also of one of the larger Cervidge, and certain cetacean bones. 

 Of iish bones there are a few vertebra of sharks and other fishes, and many 

 shark's teeth. Lying upon the surface of the river rock are also the same 

 mammalian bones, with the addition of those of the walrus, dugong, manatee, 

 mylodon, megatherium, and cetacean bones in large numbers ; also a few rep- 

 tilian vertebrae which have never been identified, while, embedded in its mass, 

 are a vast multitude of shark's teeth and a few of their vertebrae. 



There is that marked difference between these two kinds of bones, the mam- 

 malian and the fish, that, within the writer's observation, he has never seen an 

 instance of a mammahan bone being embedded and held fast in the rock, either 

 land or river, while he has in his possession several specimens where both the 

 teeth and the vertebrae of sharks and other fishes are held in the rock. 



The inference which he thinks can be legitimately deduced from this is, that 

 the formation of the phosphate deposit was contemporaneous with the partial 

 extinction in these waters of the shark family of fishes. This may have been 

 anterior to the existence here of the other classes of vertebrates. The question 

 however is unimportant, as, from the deposit having been formed under wa- 

 ter, fishes alone can be considered as having contributed to its formation. 



It is well known that the great store house of phosphorus is the earthy mat- 

 ter of bone, and here it may be objected that the skeletons of sharks being 

 largely cartilaginous, thek bodies would have been incapable of supplying the 

 amount of phosphorus required. The reply to which is that, supposing the 

 same conditions to have existed in fossil sharks as prevail in the modern shark, 

 where the only parts of the skeleton that cannot be preserved on account of 

 their softness are the skull, ribs and fins, there still remained the jaws and 

 vertebral column, the latter of which in modern sharks contains almost the 

 usual proportion of earthy mat'ter as in mammals. In estimating then the 

 probable vi)lume of the bones of the column in a large fossil shark by an in- 



