Mesozoic and Cenozoic Geology and Paleontology. 7 
about 585 feet. It consists, in general, of sand or fine gravel at the top, 
with clay interstratified toward the lower part, but the sand greatly 
predominates. The surface of the rocks in the valley wherever ex- 
amined were found to be grooved and striated. The courses of the 
grooves vary from S. 30 deg. E, to 8. 25 deg. W., and accord in a gen- 
eral way, with the direction of the valley. The limits of the valley 
evidently guided the direction of the moving masses which produced 
the strie, 
Prof. Leo Lesquereux* described, from the Pliocene near Sommer- 
ville, Fayette county, Tennessee, Salix densinervis, Quercus saffordi, 
Andromeda dubia, and Eleagnus inequalis. 
In 1860, Prof. E. W. Hilgard}+ divided the Tertiary of Mississippi 
in ascending order into, Ist, The Northern Lignitic Group; 2d, The 
Claiborne Group; 3d, The Jackson Group; 4th, the Vicksburg Group; 
dth, The Grand Gulf Group. 
The Northern Lignitic Group occupies the central part of Northern 
Mississippi, and though generally covered by later deposits it out- 
crops at numerous places and is found at alldeep borings. It consists 
of estuary deposits of sandstone, with marine shells; gray clays and 
sands, and dark brown .and yellow clays and sands with lignite. 
Kstimated thickness, including the Claiborne Group, 425 feet. 
_ The Claiborne Group is found in the central part of the northern 
half of the State, in Holmes, Atala, Carroll and Choctaw counties, and 
in the western part of the State in Clarke, Lauderdale, Newton and 
Scott counties. It consists of blue and white marls, the latter always 
sandy and often indurate, and sandstones and claystones with some- 
times lignitic clays and sands. 
The Jackson Group forms a band across the central part of the State 
through Wayne, Clarke, Jasper, Newton, Scott, Madison and Yazoo 
counties. It consists of white (often indurate) and blue marls, highly 
fossiliferous. Estimated thickness, 80 feet. | 
The Vicksburg Group is the highest of the marine Kocene, and the 
only one which reaches the Mississippi river. It occupies a narrow 
_ belt of nearly uniform width, south of the Jackson Group, and extend- 
ing across the State from Vicksburg to the Alabama line, and thence 
to the Tombigbee river, where it forms the bluff at St. Stephens. It 
consists of crystalline limestones and blue marls with ferruginous 
strata. It is the only one of the marine stages of the Eocene which 
* Am. Jour. Sci. & Arts, 2d ser., vol. xxvii. 
+ Geo. of Miss. , 
