PLATE VI. 
DIPHYPHYLLUM ARUNDINACEUM, Billings. Nat. size. (p. 32.) 
SyRINGOPORA LAXATA, Billings. Nat. size. (p. 41.) 
AULOPORA TUBAFORMIS, Goldfuss. Nat. size. (p. 43.) 
AULOPORA UMBELLIFERA, Billings. An unusually large example. Nat. size. 
(p. 43.) 
ERIDOPHYLLUM SimMcoENSE, Billings. Nat. size. (p. 34.) 
CysTIPHYLLUM SENECAENSE, Billings. A decorticated and weathered specimen, 
showing the peculiar composition of the coral out of successive invaginated 
conical layers. Nat. size. (p. 35.) 
CysTIPHYLLUM SULCATUM, Billings. Nat. size. (p. 38.) 
CystipHyLLuM AmeEricaNuM, Edw. & H. A small specimen from the Corni- 
ferous Limestone. Nat, size. (p. 36.) 
