GEOLOGY AND PALEONTOLOGY OF THE CANAL ZONE. 387 



several teeth with rounded upper ends. The youngest septa are 

 largely composed of ascending spines which are not completely fused . 



Columella relatively large, composed of septal trabecular, upper 

 surface coarsely papillate. 



Endothecal dissepiments highly developed, forming curved vesicles. 

 Exotheca composed of successive, superposed but separated plat- 

 forms extending between corallites (see pi. 90, fig. lc). 



Localities and geologic occurrence. — Georgia, stations 3881, Blue 

 Spring, 4 miles below Bainbridge, and station 3883, Hales Landing, 

 7 miles below Bainbridge, Flint River, Decatur County, collected by 

 T. W. Vaughan; in the basal part of the Chattahoochee formation, just 

 above the contact with the Ocala limestone. In the base of one 

 specimen from station 3383 there is a cast of the surface of Cerithium 

 vaughani Dall, and there are several specimens of orbitoidal foram- 

 inifera, one of which is clearly a species of Lepidocyclina. Stations 

 6085, Withlacoochee River, a few hundred yards below the Val- 

 dosta Southern Railway bridge, and 6084, about 3 miles below the 

 same bridge, Lowndes County, Georgia, collected by L. W. Stephen- 

 son. 



Type.— No. 324881, U.S.N.M. 



Santo Domingan specimens, representing a very closely related if 

 not identical species, were obtained by Miss C. J. Maury, on Rio 

 Cana, in what she refers to as zone H, in association with a fauna 

 representing the Bowden horizon, namely, Placocyathus new species, 

 Stylophora granulata Duncan, Antillia bilobata Duncan, OrbiceUa lim- 

 bata (Duncan), Solenastrea bournoni M. Edwards and Haime, Syzy- 

 gopliyllia gregorii (Vaughan), and Siderastrea siderea (Ellis and 

 Solander) . 



9. ORBICELLA COSTATA (Duncan). 



Plate 91, figs. 1, la, 2, 3, 3a; plate 92, figs. 1, 2, 3; plate 93, figs. 1, la. 



1863. Astraea coslata Duncan, Geol. Soc. London Quart. Journ., vol. 19, p. 422, 



pi. 13, fig. 9. 

 1867. Heliastraea costata Duncan, Geol. Soc. London Quart. Journ., vol. 24, p. 24. 



Original description. — "The specimens of this species which I have 

 examined present polished longitudinal and transverse sections of 

 corallites, but I have seen no calices. Corallites long, parallel, some- 

 times deformed, generally circular in transverse outline, not crowded, 

 but close, varying in size. Intercorallite spaces very distinct. Walls 

 thin, not thicker than the delicate septa. Costae large alternately, 

 both sizes equally produce'd; wedge-shaped at the wall, pointed, and 

 often bent at the free end. Septa all delicate and linear near the 

 columella and in the middle; at the wall their base is narrower than 

 that of the costae. They are arranged in six systems, the cycles 

 being very irregular. In three systems there are three cycles, and 

 in the rest an incomplete fourth; rarely there are two systems with 



