EXOGYEA COSTATA ZONE. 



37 



Species characteristic of Liopistha protexta subzone. 



E chino d errnata : 



Hemiaster lacunosus Slocum. 

 Molluscoidea: 



Terebratulina floridana (Morton). 

 Mollusca: 



Cucullasa vulgaris Morton. 



Exogyra costata Say (variation with narrow, strong 

 costse) . 



Trigonia thoracica Morton. 



Pecten venustus Morton. 



Plicatula urticosa (Morton). 



P. sp. nov. 



Liopistha protexta Conrad. 



Crassatellites vadosa Morton. 



Delphinula lapidosa Morton. 



Mollusca — Continued. 



Perissolax octolirata (Conrad). 



Scala sillimani (Morton). 



Gyrodes petrosa (Morton). 



Xenophora leprosa (Morton). 



Turritella vertebroides Morton. 



Bulla mortoni Forbes. 



Nautilus dekayi Morton. 



Baculites eolumna Morton. 



B. labyrinthicus Morton. 



B. tippaensis Conrad. 



B. carinatus Morton. 



Scaphites conradi (Morton) (varieties). 



Hamites sp. nov. 



Belemnitella americana (Morton). 



The Liopistha protexta, subzone is traceable from the Selrna chalk into the Ripley formation, 

 both northward in Mississippi and eastward in Alabama. In each direction there seems to be 

 some expansion in the vertical ranges of most of the characteristic species, rendering the limits 

 of the subzone less definite in the Ripley type of materials than in the Selma chalk. 



EXTREME UPPER CRETACEOUS BEDS. 



In places in the eastern Gulf region certain faunal elements, which seem to indicate a slightly 

 higher stratigraphic position and a slightly younger age for the beds containing them than that 

 of the Liopistha protexta subzone, appear in the extreme uppermost beds of the Cretaceous in 

 association with large numbers of other species common to the underlying beds. This horizon, 

 however, is within the zone of Exogyra costata. The exposures on Chattahoochee River from 

 Alexanders Bluff, 8 miles below Eufaula, to the mouth of Pataula Creek, and the exposures at 

 the ' ' Narrows " of Pataula Creek, 2 miles above its mouth, fall within this class. These newly 

 introduced elements are represented by the following forms: 



Newly introduced species in extreme uppermost beds of the Cretaceous. 



Echinodermata: 



Cassidulus porrectus Clark. 



C. subconicus Clark. 



C. conoideus Clark. 

 Mollusca: 



Cucullsea littlei (Gabb). 



Mollusca — Continued. 



Breviarca cuneata (Gabb). 



Anomia ornata Gabb. 



Cardium eufaulense Conrad (a large varietal form). 



Linearia sp. nov. (from Pataula Creek, Ga.). 



Turritella sp. nov. (with two spiral ridges). 



Indications of this higher horizon have also been noted in cuts north of Fort Deposit in 

 Lowndes County, Ala., in an exposure a mile south of Houston, in Chickasaw County, Miss., 

 and in an exposure 3 miles south of New Albany in Union County, Miss. 



CORRELATION OF THE ZONE. 



INVERTEBRATES. 



The C'arolinas. — The zone of Exogyra costata of the eastern Gulf region finds its counterpart 

 in the Peedee sand of the Carolinas. Typical specimens of Exogyra costata make their first 

 appearance in the basal beds of the Peedee sand and range to its summit. The fauna of the 

 Peedee is small as compared with that of the corresponding deposits in the eastern Gulf region, 

 the number of species known from the terrane being but 35. Of the 127 species restricted to 

 the zone of Exogyra costata. in the eastern Gulf region, 11 occur in the Peedee sand, and 4, 

 questionably 5, in the underlying Black Creek formation. Of the 11 species only 1 ranges 

 down into the Black Creek formation and this one is known only in the extreme uppermost, 

 beds of that formation. In contrast, the Black Creek fauna is large, including 92 known 

 species. With so large a Black Creek fauna it is significant that of the 127 species restricted 



