PLATE VI. 



Fig. 1. DIPHYPHYLLUM AKUNDiNACEUM, Billings. Nat. size. (p. 32.) 

 Fig. 2. SYRINGOPORA LAXATA, Billings. Nat. size. (p. 41.) 

 Fig. 3. AULOPORA TUB^FORMIS, Goldfuss. Nat. size. (p. 43.) 



Fig. 4. AULOPORA UMBELLIFERA, Billings. An unusually large example. Nat. size, 

 (p. 43.) 



Fig. 5. ERIDOPHYLLUM SIMCOENSE, Billings. Nat. size. (p. 34.) 



Fig. 6. 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.) 



Fig. 7. CYSTIPHYLLUM SULCATUM, Billings. Nat. size. (p. 38.) 



Fig. 8. CYSTIPHYLLUM AMERICANUM, Edw. & H. A small specimen from the Corni- 

 ferous Limestone. Nat. size. (p. 36.) 



