Mesozoic and Ca;nozoic Geology and Paloiontology. 195 



about 585 feet.. It consists, in general, of sand or fine gravel at tlie top, 

 with clay interstrati fieri 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 S. 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 strise, 



Prof. Leo Lesquereux* described, from the Pliocene near Sommer- 

 ville, Fayette county, Tennessee, Salix densinervis, Quercus saffordi, 

 Andromeda duhia, and Elceagnus inceqicalis. 



In 1860, Prof. E. W. Hilgardf divided the Tertiary of Mississippi 

 in ascending order into, 1st, The Northern Lignitic Group; 2d, The 

 Claiborne Group; 3d, The Jackson Group; 4th, the Vicksburg Group; 

 5th, 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 all deep borings. It consists 

 of estuar}^ deposits of sandstone, with marine shells; gray clays and 

 sands, and dark brown and yellow clays and sands with lignite. 

 Estimated 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 clay stones with some- 

 times lignitic clays and sands. 



The Jackson Group forms a band- across tlie 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 Eocene, and the 

 only one which reaches the Mississippi river. It occupies a narrow 

 belt of nearl}^ uniform width, south of the Jackson Group, and extend- 

 ing across the State from Vicksburg to the Alabama line, and thence 

 to theTombigbee river, where it forms the bluff at St. Stephens. It 

 consists of crystalline limestones and blue marls with ferruginous 

 strata. It is the'onl3^ one of the marine stages of the Eocene which 



* Am. Jour. Sci. & Arts, 2d ser., vol. xxvii. 

 + Geo. of Miss. 



