[ 237 ] 70 



characters, that which has been named cliff limestone by Dr. Locke in 

 his Report on the Geology of the State of Ohio, and which has been 

 more recently again described by Dr. Owen in his Report on the Mineral 

 Region of Illinois and of Iowa.* Should the two rocks be identical, 

 No. 2 of the preceding section would then be the equivalent of the 

 Western blue limestone of these geologists ; with the difference, that the 

 two rocks are here less developed than in the other localities observed by 

 them. 



3. Soil, consisting of sand, gravel, and clay, mixed with the disintegra- 

 tion of the limestone in place, and amidst which there are erratic blocks 

 scattered over the plains and on the slopes of the hills, and which are 

 traced to the summits of the Pilot Knob. 



I do not deem it necessary to make any further subdivision of this group 

 of rocks, which has already been described by the late Professor W. H. 

 Keating, in the account of Major Long's second expedition, as well as by 

 Mr. G.VV. Featherstonhaugh, in his official "Report of a Geological Re- 

 connoissance," (fee. ; and by Mr. W. W. Mather, in another report, also in- 

 tended to be official, but never published, and which he has been kind 

 enough to communicate to me. 



We may differ as to the exact position of this group of rocks in the 

 geological series ; but as this is a matter to be decided by reference to its 

 fossil contents, 1 refer the geological reader to appendix C, in which I 

 have given an ample catalogue of those collected by me from the St. Pe- 

 ter's to the Falls of St. Anthony. There are among them some new- 

 species, that should be described and figured. 1 have been assisted in 

 the determination of them by my friend Mr. T. A. Conrad, whose well- 

 known skill as a palaeontologist will be a sufficient guarantee of its ac- 

 curacy. I may remark here, that it will be seen that this list of fossils 

 embraces a iew species of the Trenlon limestone, as described by the 

 New York geologists; whence we might infer that the group of St. Pe- 

 ter's characterizes a rock of the same age as that which contains the lead 

 at Galena, and which may probably be an upper portion of the Trenton 

 limestone, newer than any part of that formation hitherto observed in the 

 State of New York. To complete the catalogue, I have added to it a 

 list of the Galena fossils, of which I possess an interesting collection, 

 embracing some valuable specimens given to me by my friend Dr. H. 

 King. Those interested in the subject will«thus be enabled to compare 

 the formations at St. Peters with those of Galena, and test the accuracy 

 of the geological deduction expressed above. On the other hand, as it is 

 always necessary to have as great a number of fossils as possible, when 

 we wish to identify formations at a great distance from each other, these, 

 added to those published by Dr. Owen and Dr. Locke, may, perhaps, aid 

 in a comparison of the rocks of the west with the silurian system de- 

 scribed by the New York geologists, and perchance throw some light on 

 the connexion that exists between these and the other stratified rock,s 

 of this continent, as well as those of Europe. The fossils are classified 



♦ The friend-; of science and the people of the west have reason to regret that this valuable 

 report has not been published wiih the necessary diagrams, which the author had prepared to 

 illustrate his text ; and that Congress did not see fit to grant the appropriation asked by the 

 Secretary of the Treasury for the republication of a second and more complete edition. 



