GEOLOGY. 305 



worms. In the Berlin Monats-Bericht, for July, 1855, Ehrenberg gives an 

 account of very perfect casts of jSTummulites, from Bavaria and from France, 

 showing not only chambers connected by a spiral siphuncle, but also a com- 

 plicated system of branching vessels. He also gave at the same time an 

 account of a method he had applied for the purpose of coloring certain glass- 

 like casts of Polythalamia, which he had found hi white tertiary limestone 

 from Java. This method consists in heating them in a solution of nitrate of 

 iron, by 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 observ- 

 ations 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 Mullica Hill, and near Mount Holly, is 

 very rich in Greensand casts of Polythalamia and of the tubuliform bodies 

 above alluded to. 2d. Cretaceous rocks from Western Texas yielded a con- 

 siderable number of fine Greensand and other casts of Polythalamia and 

 Tubuli. 3d. Limestone from Selma, Alabama gave similar results. 4th. 

 Eocene limestone from near Charleston, S. C., 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, &c., of 

 Polythalamia, Tubuli, and of the cavities of Corals, were found in the specimen 

 of yellowish limestone, adhering to a specimen of Scutella Lyellii from the 

 Eocene of North Carolina. 7th. Similar casts of Polythalamia, Tubuli, and 

 of the cavities of Corals, and species of Encrinitis, were found abundantly in a 

 whitish limestone adhering to a specimen of Ostrea sellseformis from the 

 Eocene of South Carolina. The last two specimens scarcely gave any indica- 

 tions 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 Pourtales, upon some specimens of soundings 

 obtained by the U. S. Coast Survey in the exploration of the Gulf Stream, 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, proba- 

 bly 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, I have found that not only is 

 Greensand present at the above locality, but at many others, both in the Gulf 



