ON THE 



u p p i: r 



MISSISSIPPI. 



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appear, and continue for a mile and a half, interrupted occasionally by the last 

 partial uplifts of magnesian limestone. 



No true carboniferous limestone was discovered here, but, two miles below 

 Hampton, limestones of the Devonian system crop out in ledges about six feet high. 

 The rock is almost white, of an exceedingly close texture, and effervesces freely 

 with acids. In appearance it resembles the Bird's-eye Limestone of Kentucky ; 

 some layers have small crystalline spots, arising from the presence of a serpuliform 

 coral, probably belonging to the genus Syringopora, which is shown more distinctly 

 on the weathered surface of many of the slabs. Associated with this fossil, we 

 found some imperfect specimens of Terebratula and Loxonema (?) . 



A short distance below this exposure, on the same bank of the river, are nume- 

 rous boulders, of granite, gneiss, and greenstone porphyry, some of which are several 

 feet in diameter. 



About three and a half miles below Hampton, the white compact limestone again 

 reaches the surface, forming a low ledge, elevated only one foot above the water- 

 level. 



A few hundred yards further down stream masses of yellow sandstone are strewn 

 along the shore ; and a short distance below, an ash-coloured, calcareo, siliceous grit 

 crops out in thin layers, full of Lepidodendra, Ccdamites, Sphenopteris, and Pecop- 

 teris, some of them beautifully preserved. The beds were too close to the water's 

 edge to ascertain the relative stratigraphical position of these sandstones and 

 shales. 



A quarter of a mile still further down the river, the white limestone is again 

 exhibited, in ledges fifteen feet high, with a dip to the northeast of about 3°. One 

 of the beds, five feet above the water-level, contains a profusion of small Spirifers, 

 which appear to be identical with Spirifer glabra of Sowerby. 



From this point, the white compact limestone is almost constantly exposed, to 

 Davenport, with an elevation varying from eight to fifteen feet, and usually in per- 

 pendicular walls. Just before reaching the mouth of Duck Creek, the strata assume 

 a massive character, and exhibit, on the weathered surface, remains of CyathophyTla 

 and other genera of Polyparia. 



At Davenport, directly on the river, the white limestone appears in a perpendi- 

 cular wall, ten feet high. Back from the river, at Le Claire's quarry, higher beds 

 have been laid bare. The base of the quarry is forty-four feet above the water-level 

 of the Mississippi, and the white limestone is seen extending to the height of fifty-four 

 feet, ten feet being exposed in the quarry. The lower layers here contain numerous 

 Devonian species of fossils, viz., Atrypa reticularis, A. aspera, Chonetes nana, Orthis 

 resiipinata, Astrea ananas, A. hexagonum, Favosites polymorplm, F. spcmgitcs, /Spirifer, 

 two species, and an undetermined species of Pentamerus, together with other forms, 

 characteristic of the shell and coralline beds of the Falls of Ohio, now regarded as 

 equivalent to strata of the Devonian epoch of Europe. 



The upper layers of the quarry are highly charged with remains of Crinoidea ; in 

 fact, some portions of the rock are almost entirely composed of the columns of these 

 animals. It is rare, however, to find the visceral cup. We found here only four 

 specimens of this part of the Crinoid, and these crushed specimens of Hexacrinus. 



