54 SPECIES OF EXOGYRA FROM THE EASTERN GUEF REGION AND THE CAROLINAS. 



Geologic occurrence. — This variety makes its first appearance approximately coincident with 

 the initial appearance of the typical, strongly costate forms ; that is, at the base of the zone of 

 Exogyra costata; it has not been found in association with typical specimens of Exogyra pon- 

 derosa Roemer. In the lowermost beds of its stratigraphie range, especially in Mississippi, it 

 appears to exceed in numbers the typical costate forms. In the successively higher beds it 

 appears to decrease in numbers, and it is absent, so far as known, from the upper 80 or 100 feet 

 of strata in Mississippi and western Alabama and probably from a somewhat greater thickness 

 in the Chattahoochee region. 



In the Carolinas the form occurs in the Peedee sand, the known localities being near the 

 base of that terrane; that is, near the base of the zone of Exogyra, costata. 



Among the collections in the National Museum are specimens of this variety labeled as 

 follows: 



U. S. Geol. Survey coll. 288c— Cretaceous (Middle marl), near St. Georges, Del. Collector, J. B. Marcou. [2 

 specimens.] 



U. S. Geol. Survey coll. 286. — Cretaceous. New- Egypt, N. J. Collector, J. B. Marcou. [12 or more specimens.] 

 U. S. Nat. Museum Cab. No. 21778.— New Jersey, part of O. N. Bryan collection, March 18, 1892. 



The St. Georges specimens probably came from an exposure on or near the Chesapeake 

 and Delaware Canal. The specimens from Xew Egypt are associated with Cucullsea antrosa 

 Morton, Exogyra costata Say (typical), Gryphsea vesicularis Lamarck, Veniella conradi (Morton), 

 Cardium spiUmani Conrad, and Belemnitella americana (Morton); the collection probably came 

 from a Monmouth horizon (possibly the Xavesink marl of the Monmouth group) within several 

 miles north or northwest of New Egypt, Ocean Count} - : for according to the geologic map of 

 New Jersev only strata of the Rancocas and Manasquan formations, from which no representa- 

 tives of Exogyra have been reported, outcrop in the immediate vicinity of New Egypt. The 

 collection has the aspect of a Navesink marl fauna. 



In Arkansas the variety occurs abundantly in the Marlbrook marl. 



In Texas the variety has been obtained from three localities, all of which are probably near 

 the base of the Navarro formation. The first locality is one-half mile north of Cooper, Delta 

 County (U. S. Geol. Survey colls. 4064 and 7509) and the second and third are 4 and 4^ miles, 

 respectively, east of Crandall, Kaufman County (U. S. Geol. Survey coll. 7549). 



Three typical specimens of this variety, brought from Mexico in 1906 by Dr. T. W. Stanton, 

 were given to him at San Luis Potosi and were said to have been collected from a locality (U. S. 

 Geol. Survey coll. 4129) near Ciudad del Maiz. State of San Luis Potosi. 



Localities. — In the eastern Gulf region the variety has been obtained from 27 localities, 

 detailed descriptions of which accompany the tables (pp. 24-25). Some of the more notable 

 occurrences are the following: 



U. S. Geol. Survey coll. 6418<7-_/. — Johnsons Hill. 4 miles north of Lumpkin on Lumpkin-Louvale road, Stewart 

 County, Ga. Ripley formation. Exogyra costata zone. 



U. S. Geol. Survey colls. G413, 0414. — ( uts of Seaboard Air Line Railway, one-quarter to 1} miles north of Renfroea, 

 Stewart County, Ga. Ripley formation. Exogyra costata zone. 



U. S. Geol. Survey colls. 6790, 6792.— Alabama River, Rocky Bluff, about 1 mile above Prairie Bluff, Wilcox 

 County, Ala. Ripley formation, within 80 to 100 feet of top of Cretaceous. 



U. S. Geol. Survey coll. 6S05. — Public road, 6 miles north of Livingston, Sumter County, Ala. Selma chalk, 

 Exogyra costata zone. 



U. S. Geol. Survey coll. 647S. — Roadside exposure on Brane's plantation, 2i miles south of Macon, Noxubee 

 County, Miss. Selma chalk, Exogyra costata zone. 



TJ. S. Geol. Survey coll. 6S40. — Exposure in public road, 3 miles northwest of Macon, Noxubee County, Miss. 

 Selma chalk, Exogyra costata zone. 



U. S. Geol. Survey coll. 6862. — West Point-Cedar Bluff road, 1 mile east of Cedar Bluff near west end of bridge 

 over Line Creek, Clay County. Miss. Selma chalk, Exogyra costata zone. 



U. S. Geol. Survey coll. 6472. — Gullies south of Troy-Shannon road. 3 miles east of Troy, in Lee County, Miss. 

 Selma chalk, Exogyra costata zone. 



U. S. Geol. Survey coll. 6456. — Gullies near public road. 3A miles northwest of Booneville, Prentiss County, Miss. 

 Selma chalk near base of Exogyra costata zone. 



U. S. Geol. Survey coll. 6459.— Bald Knob, Joseph Reynolds place, 3 miles west of Corinth, Alcorn County, Miss. 

 Selma chalk, toward base of Exogyra costata zone. 



