’ 
} 
3 
Mineralogy and Geology. 283 
6th. Abundance of organic casts, in Greensand, &e., of Polythalamia, 
ubuli, and of the cavities of Corals, were found in the specimen of yel- 
lowish limestone, adhering to a specimen of Scutella Lyelli from the Eo- 
cene of North Carolina. 
7th. Similar casts of Polythalamia, Tubuli, and of the cavities of Cor- 
als, and spines of Echini, were found abundantly in a whitish limestone — 
adhering to a specimen of Ostrea sellzeformis from the Eocene of South 
Carolina. 
i n pe 
shells of Polythalamia. It appears from the above, that the occurrence 
the formation of precisely similar Greensand and other casts of Polythal- 
amia, Mollusks, and Tubuli, is now going on in the deposits of the pres- 
ent ocean. 
homs, is mentioned as “a mixture in about equal proportions 
Globigerina aud black sand, probably greensand, as it makes a green mark 
when crushed on paper.” Having examined the specimen alluded to by 
Mr. Pourtales, besides many others from the Gulf Stream and Gulf of 
Mexico, for which I am indebted to Prof. A. D. Bache, the Superintend- 
ent of the Coast Survey, I have found that not only is Greensand present 
at the above locality, but at many others, both in the Gulf Stream and 
. Gulf of Mexico, and that this Greensand is often in the form of well-de- 
fined casts of Polythalamia, minute Mollusks, and branching Tubuli, and 
Ww 
hite. In some cases I have noticed a single cell, of a spiral Poly- 
