PLATE LIII. 
G-YROCERAS UNDULATtTM. 
Page 378. 
See Plate 54. 
Pig. 1. Lateral view of a specimen showing the number of the volutions'and the nodes on.the internal mould, 
corresponding to the subtubular expansions or spines on the test. Upper Helderberg lime¬ 
stone. Cherry Valley, N. Y. 
Figs. 3, 4. A septum and transverse section of a fragment, which is compressed, and does not show the 
natural broadly ovate, subtriangular form of the tube. 
Fig. 5. A section of the disc of an example, showing the depth of the air-chambers, where the walls of the 
tube and the septa have not been destroyed. Cherry Valley, N . Y. 
Fig. 6. Another septate fragment, showing the regularity in the depth of the air-chambers. Cherry^Val- 
ley, N. Y. 
