[ 237 ] 38 



may travel over Ihis region, I signalize them by their mineralogical char- 

 acters. 



1. A cylindrical limestone, resembling arragonite. 



2. Limestone of loose texture, yellow, crossed by small and numerous 

 veins of calcareous spar. 



3. Limestone of a grayish color, with veins of calcareous spar, and in- 

 vested occasionally by dog-tooth spar. [C. carb. metastaslique of Haiiy.] 



4. Grayish limestone, with veins of calcareous spar. 



The interior members of the group that I have just described contain, it 

 is true, but rare and indistinct organic remains. But no richer field could 

 be offered to the fossil conchologist than that presented by the upper por- 

 tions of the plastic clay — by the variety, the abundance, and the beauty of 

 the specimens ; being nearly all new species of ammojiites, baculUes, be- 

 lemiiii.es. fnpjJOtvj.r, cytherea, f.cllina, inoceramus, ^'c. The species, how- 

 ever, which, from its abundance, and the different signs under which it is 

 found, would seem to me to characterize the whole formation, is the inoce- 

 ramus barabini of Morton. 



In appendix C of this report, will be found a list of the fossils in my col- 

 lection, belonging to the cretaceous formation in the Missouri, the descrip- 

 tion and figures of which are given in the Sth volume (1842) of the Jour- 

 nal of the Academy of JNatural Sciences, Philadelphia; to which I beg 

 leave to refer, with my warmest acknowledgments, at the same time, to my 

 learned and modest friend, Dr. S. G. Morton, who has furnished and added 

 to it a tabular view of the organic remains hitherto discovered in the cre- 

 taceous strata of the United States. 



The cretaceous formation now under examination also contains fossil re- 

 mains of vertebrated animals. I must regret tliat opportunities failed 

 me to explore it more thoroughly in this respect. 1 succeeded in ob- 

 taining but a few specimens ; but such as my collection afforded were 

 submitted to the distinguished palocontologist (whom I am likewise proud 

 to name as a friend) Dr. Harlan, who, with his characteristic promptness, 

 furnished me with a description of them, that 1 have appended to the cata- 

 logue above cited. I have only to add, here, that the four specimens 

 there described are also found in the Atlantic cretaceous beds of the 

 United States; thereby confirming the contemporaneity of the chalk 

 formation of the west with that of the east on the continent of North 

 America. 



This cretaceous formation may be considered, I believe, as fairly ex- 

 hibiting the characteristic features in the geology of the Missouri, over 

 an extent of country more than 400 miles in length by water, starting 

 from the mouth of Sioux river ; which latter river is 795 miles from the 

 confluence of the former with the Mississippi to the approach of the 

 Shayen ; which I have laid down on my map as the M'aslitey, or Good 

 river of the Sioux. It will be readily conceived that, as the level of the 

 valley of the Missouri gradually rises, there is a corresponding depression 

 in that of the formation. But what remains of it at the spot where I 

 left it, conjoined to information gathered, leads me to suppose that other 

 traces of it will be found, perhaps, not far from the Yellow Stone river ; 

 so that its whole extent along the Missouri, in a generally NW. course, 

 would be no less than 1,000 miles. As to its western limits, without pre- 

 tending to define these positively, I may state that I have in my possession 

 interesting fragments oi ammonite jylacenta and baculite ovatus, brought to 



