SELMA CHALK. 
17 
Fossils are more or less abundant throughout the formation. Ostrea, Gryphtra, and Exo- 
gyra are almost always present, and numerous other forms occur in the upper and lower sub- 
divisions. Below is a list of the Selma fossils reported from Mississippi by Dr. T. W. Stan- 
ton. In speaking of these fossils Stanton remarks: 
The list of fossils from the Selma or ' ' Rotten limestone 'is based on a small collection from S tarkville 
received from you and a somewhat larger collection obtained by myself at Houston. Both these locali- 
ties are comparatively near the contact of the Selma with the Eocene in an area where the Riplej as 
such does not appear. From this fact and from the close resemblance of the faunas, which would appar- 
ently be more striking if the condition of the fossils would permit the identification of all the species 
present, I am inclined to believe that the so-called ' ' Rotten limestone " of these localities is really equi \ra- 
lent to a part of the Ripley farther north. Hilgarda mentions similar occurrences in Noxubee and 
Kemper counties. 
It is very probable that thorough systematic collecting in the Selma would show some distinctive 
species. The rare fossils mentioned by Hilgard as Radiolites and " Ichtyosarculites " and several of the 
genera of fishes and other vertebrates have not been reported from the Ripley, but their presence isprob 
ably due to the difference in physical conditions rather than to difference in age. It will be noticed 
that a few of the invertebrates in the following list do not appear in the Ripley list, but nearly all of 
these species are elsewhere found in the Ripley. 
Fossils from the Selma chalk at Houston and Starkville. 
Hemiaster. 
Terebratulina. 
Ostrea larva Lamarck. 
Ostrea vomer Morton. 
Exogyra costata Say. 
Gryphsea vesicularis Lamarck. 
Anomia argentaria Morton. 
Plicatula saffordi Conrad. 
Dianchora cchinata (Morton). 
Pecten quinquecostata Sowerby?. 
Pecten venustus Morton. 
Lima acutilineata Conrad. 
Lithophagus ripleyanus Gabb. 
Nemodon eufalensis (Gabb). 
Cucullsea vulgaris Morton. 
Nucula perequalis Conrad. 
Leda longifrons Conrad. 
Trigonia thoracica Morton. 
Crassatella. 
Cardium. 
Veniella conradi Morton. 
Legumen planulatum Conrad. 
Liopistha protexta (Conrad). 
Liopistha (Cymella) bella Conrad. 
Gastrochaena americana Gabb?. 
Scala sillimani (Morton). 
Scala annulata (Morton). 
Turritella. 
Xenophora umbilicata (Tuomey). 
Pugnellus densatus Conrad. 
Gyrodes petrosa (Morton). 
Perissolax octolirata (Conrad). 
Pyropsis. 
Rostellites. 
Volutomorpha. 
Nautilus dekayi Morton. 
Baculites anceps Lamarck. 
Scaphites conradi (Morton). 
Placenticeras. 
Belemnitella americana (Morton). 
The thickness of the Selma as determined by many deep-well borings throughout the 
region is found to vary from 350 feet near the Tennessee line to 1,000 feet at Starkville and 
to over 1,200 feet just across the State line in Alabama. 
The area of the outcropping Selma is a level or rolling prairie, well adapted to agricul- 
ture. It is everywhere marked by a rich black prairie soil, which is readily formed from 
the underlying limestone. It embraces the large part of Noxubee, western Lowndes, east- 
ern Oktibbeha, the larger part of Clay, western Monroe, eastern half of Chickasaw, almost 
all of Lee, western Prentiss, and central Alcorn counties. The west line of outcrop can be 
traced approximately through Scooba, Flatwood, and a point 3 miles west of Starkville to 
Houston. From this place the line bends more to the east, passing through Troy, Blue 
Springs, Graham, Antioch, and a point 2 miles west of Kossuth to the Tennessee line. 
A description of the contact between the lower Selma and the underlying Utah, as shown 
in the river bluff 4 miles above Columbus, is given under the Eutaw formation (p. 14). At 
the above-mentioned place the ledges of indurated greensand carrying Eutaw fossils gradu- 
ally change to the blue argillaceous joint clay of the Selma. A short distance west of the 
river the typical black prairie soils of the Selma come to the surface. 
a Geology and Agriculture of Mississippi, 1860, p. 82. 
Bull. 283—00 2 
