366 



peculiar species of natural injection, 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 Zeu- 

 glodon 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, re- 

 sembling casts of the holes made by burrowing sponges (Cliona) 

 and worms. 



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

 an account 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 ves- 

 sels. He also gave at the same time an account of a method he 

 had applied for the purpose of coloring certain glasslike 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 

 different shades of yellow and brownish red, still retaining suffi- 

 cient transparency when mounted in balsam to show the connec- 

 tion 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 Holly, is very rich in Greensand casts of Poly- 

 thalamia 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. 



4lh. Eocene limestone from Drayton Hall, near Charleston, 

 South Carolina, gave abundance of similar casts. 



