■[Iti2, 16) | AGE OF NORTHERN MGNITIC. 109 



1(32. The only doubt as to the stratigraphical position of the members of thi^ 

 series, exits with reference to the strata designated as the Lignitic of North 

 Mississippi. The conformation of the surface, the scarcity of fossil remains, and 

 the variability of the strata, both as to thickness and lithological character, render 

 a direct determination of the stratigraphical relations between this group and 

 the calcareous tertiary, extremely difficult. While there can be no doubt 

 whatsoever, as to the position of stratum No. 1, the equivalence of No. 1* to the 

 same still remains to be proven by a comparison of the respective floras, for 

 which, thus far, the materials are incomplete. For the determinations of genera 

 and species of plants given in the table, I am indebted to the kindness of Leo 

 Lesquereux, Esq., of Columbus, Ohio. Thus far, however, only the fossils of 

 locality « (Red Shale) have been specially studied by him, and it remains 

 doubtful how far the Moras of the respective districts may be related. Although 

 not susceptible, at present, of strict, direct stratigraphical proof, the probable 

 equivalence of the lignitic beds underlying the siliceous strata of the Claiborne 

 age, in Lauderdale, and of those overlying the Upper Cretaceous in N. Mississippi 

 certainly impresses itself strongly upon the mind of the observer in the field. 

 An uninterrupted belt of lignitic strata, often outcropping, and always reached 

 in wells, extends along the W. border of the cretaceous territory [where it 

 gives rise to the Elatwoods (flG'i),] from the Tennessee line to the northern 

 border of the marine tertiary. The strata show no observable dip in this 

 direction, until we reach the region last mentioned, where they disappear under 

 the marine siliceous claystones and sandstones on the E. half of the territory, 

 and under the calcareous marls on the W. On the whole of this line, there is 

 no more change of litlbblogical character, than may be observed in almost any 

 single locality ; even to the minute particulars, the same phenomena which we 

 saw in Tippah, Marshall, Pontotoc, Lafayette and Calhoun, may be observed in 

 Choctaw, Winston, Kemper and Lauderdale. 



163. Several of the plants from the red shale (locality a) determined by Mr. 

 Cesipiereux, are considered peculiar to the Miocene of Europe ; the rest appear 

 to be analogous at least, and would therefore place the strata containing them 

 ribove the marine tertiary of the State — assumed to be of eocene age, and cer- 

 tainly not referrible to any newer stage, since it does not contain a single fossil 

 identical witli living species. — On the other hand, we find in N. Tippah, on the 

 border of the cretaceous formation, a limited stratum of siliceous sandstone, 

 undistinguishable, lithologically, from that found on the territory of the Siliceous 

 Claiborne stage, uuderlaid and overlaid by gray Lignitic clays, similar in all res- 

 pects to that of the rest of Tippah, and connected with the latter by numerous 

 outcrops, although the stratum is not strictly traceable. The rock mentioned 

 contains Venericurdia plant costa ■!, Cardium Nicolleti?, and other fossils, appa- 

 rently peculiar ; whence it appears that this estuary deposit, at least, is of 

 eocene age — and with it, we should naturally presume, the rest of the lignitic 

 clays of Tippah and Pontotoc, whose highest strata frequently exhibit a ledge of 

 rock of a similar character, in which ill preserved remnants of marine fossils are 

 occasionally, though rarely, found, together with grains of greensand (^"166). 

 Near Shongalo, Carroll county, also, there occurs a deposit of marine origin, 

 with fossils corresponding to the Claiborne stage, which is certainly underlaid, 

 and probably also overlaid by lignitic clays, the territory of which surrounds it 

 on all sides (see map). The imperfect state of preservation of most of the fos- 

 sils of the estuary deposit of Tippah, just mentioned, render its identification 

 with any particular stage of the eocene somewhat difficult. — It appears, how- 

 ever, from extensive comparisons made by Prof. W. D. Moore, of the number of 

 ribs found in Vmericardia planicosta from different geological horizons, that the 

 average number of ribs in that fossil decreases in proportion as we descend in 

 the series ; as exhibited in the following table : 



