Miscellaneous* 427 



means of which they can be made to assume different shades of 

 yellow and brownish-red, still retaining sufficient transparency when 

 mounted in balsam to show the connexion of the different parts. 



The interesting observations of Ehrenberg, which are alluded to 

 above, have led me to examine a number of the cretaceous and 

 tertiary rocks of North America in search of greensand and other 

 casts of Polythalamia, &c. The following results were obtained : — 



1st. The yellowish limestone of the cretaceous deposits of New 

 Jersey, occurring with Teredo tibialis, &c., at MuUica Hill, and near 

 Mount Holley, is very rich in greensand casts of Polythalamia and 

 of the tubuliform bodies above alluded to. 



2nd. Cretaceous rocks from Western Texas, for which I am in- 

 debted to Major W. H. Emory, of the Mexican Boundary Com- 

 mission, yielded a considerable number of fine greensand and other 

 casts of Polythalamia and tubuli. 



3rd. Limestone from Selraa, Alabama, gave similar results. 



4th. Eocene limestone from Drayton Hall, near Charleston, South 

 Carolina, gave abundance of similar casts. 



5th. A few good greensand casts of Polythalamia were found in 

 the residue left on dissolving a specimen of marl from the Artesian 

 well at Charleston, S.C. ; depth 140 feet. 



6th. Abundance of organic casts, in greensand, fee, of Polytha- 

 lamia, tubuli, and of the cavities of Corals, were found in the 

 specimen of yellowish limestone adhering to a specimen of Scutella 

 Lyelli from the Eocene of North Carolina. 



7th. Similar casts of Polythalamia, tubuli, and of the cavities of 

 Corals, and spines of Echini, were found abundantly in a whitish 

 limestone adhering to a specimen of Ostrea sellceformis from the 

 Eocene of South Carolina. 



The last two specimens scarcely gave any indications of the presence 

 of greensand before they were treated with dilute acid, but left an 

 abundant deposit of it when the calcareous portions were dissolved 

 out. All the above-mentioned specimens contained well-preserved 

 and perfect shells of Polythalamia. It appears from the above, that 

 the occurrence of well-defined organic casts, composed of greensand, 

 is by no means rare in the fossil state. 



I come now to the main object of this paper, which is to announce 

 that the formation of precisely similar greensand and other casts of 

 Polythalamia, mollusks, and tubuli, is now going on in the deposits 

 of the present ocean. In an interesting Report by Count F. Pourtales, 

 upon some specimens of soundings obtained by the U.S. Coast Survey 

 in the exploration of the Gulf Stream (see Report of U.S. Coast 

 Survey for 1853, Appendix, p. 83), the sounding, from lat. 31° 32', 

 long. 79° 35', depth 150 fathoms, is mentioned as "a mixture in 

 about equal proportions of Globigerina and black sand, probably 

 greensand, as it makes a green mark when crushed on paper." Having 

 examined the specimen alluded to by Count Pourtales, besides many 

 others from the Gulf Stream and Gulf of Mexico, for which I am 

 indebted to Prof. A. D. Bache, the Superintendent of the Coast 

 Survey, I have found that not only is greensand present at the 



b 



