Scientific Intelligence. 



with a light yellowish mud. The latter is easily removed by washing atid 

 decantation. The casts thus obtained are so perfect that not only the 

 genus, but often the species of the Polythalamia, can be recognized. 

 Mingled with these are frequently found spiral or corkscrew-like bodies, 

 which Ehrenberg considers as casts of the shells of young mollusks. 



With reference to the perfection of these casts of the Polythalamia, and 

 the light they throw upon the structure of these minute animals, Ehren- 

 berg remarks : — 



"The formation of the Greensand consists in a gradual filling up of the 

 interior space of the minute bodies with a green-colored, opal-like mass, 

 which forms therein as a cast. It is a peculiar species of natural injec- 

 tion, and is often so perfect, that not only the large and coarse cells, but 

 also the very finest canals of the cell walls, and all their connecting tubes 

 are thus petrified, and separately exhibited. By no artificial method can 

 such fine and perfect injections be obtained." 



Having repeated the experiments of Ehrenberg upon the Zeuglodon 

 limestone, I can confirm his statements in every particular, and would only 

 add, that besides the casts of Polythalamia and small spiral mollusks, there 

 is also a considerable number of green, red, and whitish casts of minute 

 anastomosing tubuli, resembling casts of the holes made by burrowing 

 sponges (Cliona) and worms. 



In the Berlin Monatsbericht, for July, 1855, Ehrenberg gives an ac- 

 count of very perfect casts of Nummulites, from Bavaria and from France, 

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

 complicated 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 in 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 differ- 

 ent shades of yellow and brownish red, still retaining sufficient transpa- 

 rency when mounted in balsam to show the connection 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 Mullica Hill, and near Mount Hol- 

 ley, is very rich in Greensand casts of Polythalamia and of the tubuliform 

 bodies above alluded to. 



2d. Cretaceous rocks from Western Texas, for which I am indebted to 

 Major W. H. Emory, of the Mexican Boundary Commission, yielded a 

 considerable number of fine Greensand and other casts of Polythalamia 

 and Tubuli. 



3d. Limestone from Selma, Alabama, gave similar results. 



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

 lina, 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. 



