ON THE UPPER MISSISSIPPI. 



505 



lobite, referable, probably, to Splicer exoclms, and probably of an undescribed species. 

 Three miles above Savannah, Orihis occidental is, 0. testvdinaria, Terebratula 

 ca/pax, T. inodesta, Lepfcena sericea, L. cdternata, L. deflecta, L. planwmbona, and an 

 undetermined species of Murchisonia, Streptoplasma, Calymene senaria, and Chcetetes 

 lycoperdon. In addition to the above there occur here remains of Crinoidea, refer- 

 able to the family Cystidea of Von Buch. The species corresponds with that de- 

 scribed in the first volume of the Palaeontology of New York, under the name of 

 Ecliino-encrinites analiformis. The spines of the fossil are tolerably abundant; and 

 in a single specimen, the first series of plates (pelvis) still remain attached. 



On approaching Parkhurst, near the boundaries of F. 3, my local sections again 

 commence. Five miles above that place, a low ledge of light buff magnesian 

 limestone is exposed near the water-level of the river. It contains an abundance 

 of casts of columns of Crinoidea. The bodies are rare, but we succeeded in obtain- 

 ing two specimens of this portion of the animal. These approach, in the number 

 and arrangement of plates, to the genus Euccdypto-crinus, of Goldfuss. 



Two miles further, low ledges of soft, yellowish magnesian limestone appear, 

 and continue to prevail as far as Quarry Creek, which joins the Mississippi a short 

 distance above Parkhurst. Their height varies from six to twelve feet. A few 

 hundred yards above the creek, these strata occur in horizontal beds, elevated five 

 feet above the water-level, where a quarry has been opened ; and, a short distance 

 back from the river, is a second quarry, at a higher level, twenty-six feet above the 

 river. The lower layers consist of strata from four inches to a foot in thickness ; 

 to these succeed thin laminated layers, from a few lines to several inches in thick- 

 ness. 



On Quarry Creek, half a mile above the mouth, the strata form perpendicular 

 cliffs forty-five feet high. The rock is a soft magnesian limestone,'"' 1 of a light yellow 

 colour, containing small cavities, lined with crystals of quartz and calcareous spar, 

 and being easily wrought, is extensively used for the construction of buildings at 

 Parkhurst and Le Claire. The beds appear to lie horizontal. 



Between Quarry Creek and Parkhurst, a few exposures of the same beds are seen 

 near the water's edge. They dip at considerable angles, but the inclination is not 

 uniform. 



Near the lime-kiln at Parkhurst, where the strata have been laid bare sixteen 

 feet above the water-level of the Mississippi, I found a bed filled with casts of poly- 

 paria, among which I recognised Stromatopora pohjmorpha (?), and several other 

 forms which I have found in the Upper Silurian strata on Bear Grass Creek, near 



* An analysis of an average specimen from this locality yielded the' following proportion of constituents : 



Carbonate of lime, ....... 52-15 



" magnesia, . . . . . .42-10 



Oxide of iron, alumina, &c., . . . . 1-90 



Insoluble matter, .... . 1-20 



Moisture, ........ 1-55 



Loss, ...... . 110 



100-00 



