GEOLOGICAL REPORT. [TW8, 199, 200 



laid by gray laminated clays and sands (■ 204). The great thickness of this 

 lignitic stratum, as ascertained in the well bored at the Penitentiary, has already 

 been referred to (HT87). In the town of Jackson it is commonly struck in dug 

 wells, and various kinds of leaves, as well as acorns, have been found in them. 

 It is evident that the stratum thins out to the eastward, and at Claiborne, and 

 Bettis' Hill, Alabama, according to Lycll (Sill. Am. J., Vol. IV, 2d s., p. 189) and 

 Tuomey, it is entirely wanting, the Claiborne strata being immediately overlaid 

 by the Zcuglodon or Jackson bed, and this by the Orbitoides Limestone, of the 

 Vicksburg < rroup. 



III. THE JACKSON GROUP. 



1918. The territory of this group, although to a considerable 

 i occupied, like the rest, by Orange Sand ridges, is strongly 

 characterized in many regions by the occurrence of the black 

 prairie soil on its surface, and also, of bald prairies — both very 

 similar to those of the Rotten Limestone region, though of much 

 less extern. It shares this character to an inconsiderable extent 

 only, with the strata of the Vicksburg Group. The material to 

 winch Ibis prairie soil owes its origin, possesses considerable ana- 

 logy to the Rotten Limestone itself — at times, it is a soft yellowish 

 limestone or indurate marl, containing a good deal of clay; at 

 others, it is in reality, nothing more than a soft, gray or yellowish, 

 calcareous clay. The rock and clay mentioned are ordinarily the 

 matrix of the huge Zcuglodon bones, which are therefore to be 

 sought chiefly in the prairies, and have not, to my knowledge, as 

 yet been found at any ureal distance from them, in Mississippi. — 

 These bones, an oyster somewhat resembling Gryphaea convexa of 

 the Cretaceous, the vertebrae and teeth of fish, and a branching 

 '•oral (Eschara sp.) are the common fossils of the tertiary prairies 

 of S. Mississippi. 



Other bivalves and univalves, as also echinoderms, may sometimes be found 

 in a tolerably well preserved condition, in the more sandy varieties of this material; 

 but as a general thing, imperfect casts only of these occur in the prairie rock, 

 and usually it requires considerable care to detect their presence at all. 



199. About 70 feet of rocks of this character form the upper division of the 

 Jackson stage. The lower portion is formed by from 10 to 20 feet of sandy 

 strata, commonly of a bluish tint, and containing greensand grains. 



It is this lower bed, cropping out on the banks of Pearl River, at Jackson, 

 which has furnished the fossils described by Conrad, and figured in Prof. Wailes' 

 Report ; and whose state of preservation approaches very closely to that of the 

 well-known Claiborne fossils, in Alabama. I have not thus far found any vestiges 

 of the Zeuglodon in this lower division, but I have identified most of its 

 characteristic fossils in the upper strata, at various times and localities. 



200. Whilst the stratigraphical relations of this group to that next above it 

 (the Vicksburg Group) may be traced with considerabl • regularity of (southward) 

 dip, along the channels of the two rivers which cross both belts (the Chickasawhay, 

 and Pearl River), there appears to hi 1 some irregularity in the form of the 

 stratum on its northern portion. According to the levelings of the N. O., J, 

 and C5. N. If. R., the city of Jackson is situated 15 feet higher than Canton, 

 Madison county, which is distant 25 miles due N. from the former place ; by the 

 levelings of the Gulf and Ship Island Railroad Survey, however, the difference is 

 only 25 feet. At Canton, we find the highest strata, apparently, of the Jackson 

 Group — the gray calcareous clay matrix of the Zeuglodon, occupying the surface, 



