IOWA, AND WAPSINONOX RIVERS. 



79 



a mass of agglutinated remains of Polypi/era, that it may be almost considered a 

 petrified coral reef; while the upper, though not presenting so great a variety of 

 species, and at first view hardly recognisable except as a white, close-textured lime- 

 stone, is shown, under the magnifier, to be made up almost entirely of a fossil coral, 

 closely allied to the genus Stromatopora, the concentric growths of which are so 

 minutely compact, as seldom to be detected by the naked eye. To thill an excep- 

 tion must be noticed, in some of the layers immediately superimposed on the shell- 

 beds, which are characterized by a considerable variety of Cyaihqphyllidce. 

 The most commonly occurring fossil species in these three divisions are 



1. In the lower beds. Lithostrotion ananas and L. pentagonum. To the embedded 

 specimens of this beautiful, star-like polypifera is a portion of the Iowa limestone 

 indebted for that appearance of great beauty, when highly polished, which has pro- 

 cured it the name of " Iowa marble." Unfortunately it is seldom found in masses 

 sufficiently large for the usual purposes of commerce. Favosites cronigera and F. 

 Gothlandica, Stromatopora concentrica, Chatetes subfibrosa (?). 



2. Shell-beds. A large variety of Terebratula reticularis, T. aspera, T. concen- 

 trica, T. concinna (?) , Spirifer euruteines* S. mucronatus (?), and several new /Spiri- 

 fers,-\ Orthis resupinata, Lucina proavia, Phacops macroplithalma. 



3. Upper coralline beds. GyathopliyUum turbinatum (?), C. dianthus, C. ceraiites.\ 

 As yet, there have been discovered in Iowa no remains of those curious fossil 



fish, which form so singular a feature in the palaeontology of the Old Red Sandstone 

 of Scotland and Russia. The two localities in Indiana, where the Macropetalich- 

 thys was discovered (as heretofore stated in a communication from Dr. Norwood 

 and myself to Silliman's Journal), viz. : one on Lewis Creek, in Jefferson County, 

 and one at the Falls of the Ohio, in Clark County, remain, as yet, the only locali- 

 ties where rocks of that period, in the West, have furnished such remains. 



In Iowa, the opportunities are but few for studying this formation and registering 

 its fossils. The geologist who undertakes to investigate the vast prairie country 

 of the Mississippi Valley must be provided with no common share of patience and 

 perseverance. He must be content to travel for half a day together without seeing 

 aught but a rich, black soil, covered, as far as the eye can reach, even down to the 

 very edge of the small streams, with a thick and high growth of prairie grass, 

 as shown in the vignette at the close of this section, with perhaps a faint outline 

 of timber cutting the distant horizon. He must be prepared to wade swamps, to 

 ford streams waist deep, or, in times of freshets, to plunge in and breast the cur- 

 rent. He must not shrink beneath a broiling sun, without even a bush to cast a 

 faint shadow over an occasional resting-place. He must think himself fortunate if 

 he can reach, at night, a few scattered oaks to plenish his fire, and boil his camp- 

 kettle ; and he may consider it a special instance of good luck, if, in return, he can 

 catch a glimpse of a rock exposure once or twice a day. He may travel for days 

 together without lighting on any object more interesting than the hillock of the 

 prairie dog, or the broad lair of the bison. 



* Tab. iii. fig. 6. f T. iii. 



I See Appendix, for further remarks on the organic remains of these limestones. 



