Association of American Geologists. 181 



raphy of the country represented, together with the most prominent fea- 

 tures in the geology and mineral resources of other sections of our western 

 states not embraced within the limits of the map. 



Mr. N. then went on to give a succinct account of his geological re- 

 searches, which, modestly disclaiming any pretensions to be considered a 

 professed geologist, he had felt an irresistible inclination to engage in, as 

 a subject of general and growing interest. This account he offered as a 

 more appropriate theme, in view of the objects contemplated by the pres- 

 ent meeting. 



Mr. N. said he had traced a magnesian limestone — the cliff limestone 

 of Dr. Owen — which is probably referrible to the mountain limestone of 

 European geologists, over a vast extent of country, within the valley of 

 the Mississippi. Connecting his own researches with the facts brought 

 to light in the survey of the Iowa and Wisconsin Territories by Dr. D. D. 

 Owen and Prof John Locke, and with the observations of Dr. Henry 

 King, during an exploration of the country watered by the Osage river, 

 Mr. N. thought himself warranted in assigning the Falls of St. Anthony 

 on the Mississippi river, as the northern limit of this formation, which to 

 the west, extends to Fort Leavenworth on the Missouri river, and to the 

 south, embraces the metalliferous region of the state of Missouri. This 

 limestone, containing irilobites, catenipora, and other coralline fossils, is 

 the metalliferous rock not only in Missouri, but in Iowa and Wisconsin, 

 from which the lead and copper ores are extracted. The rock interven- 

 ing between it and the coal formation is characterized by the occurrence 

 of the Pentamerus oblongus. In this relative position, also are found thin 

 beds of oolitic limestone, that are perhaps referrible, geologically, to the 

 oolitic limestone of Tennessee, described by Dr. Troost, who indicates the 

 ■pentrcmites as their characteristic fossil ; a large number of these fossils, 

 in a loose state, was collected in the vicinity of these rocks. Shallow 

 coal basins frequently occur in Missouri and the south part of Iowa Ter- 

 ritory ; but on the Mississippi river, the coal disappears, about thirty miles 

 above St. Louis ; thence, ascending the river as far as the great Platte 

 river, the cliff limestone and the coal rocks present themselves in alter- 

 nate succession. In the vicinity of the Platte river, as well as at Council 

 Bluff, a limestone containing cyathophylla of large size, encrinites, and 

 other fossils, appears in a position seemingly between the cliff limestone 

 and the coal. Near the confluence of the Sioux river and the Missouri, 

 there occurs a formation overlaid by a thick deposit of clay, containing, in 

 abundance, several species of ammonites and baculitcs, btleiimites, ino- 

 cerami, &lc. &c., beautifully raised on their exterior and sparry in their 

 interior. Some of them were exhibited to the meeting. These fossils 

 were identified with similar ones belonging to the green sand deposit of 

 New Jersey, a member of the chalk series; but no true chalk or flint 

 (silex pyromage) was observed. The occurrence of this formation had 



