1 882.] Geology and Paleontology. 159 



ceras ; two undetermined species of Platycerinus ; three undeter- 

 mined species of Actinoceras. Mr. Miller remarks that the age of 

 the rocks, if all the fossils are from one range, js that of the 

 Upper Burlington or Lower Keokuk, but if of different elevations, 

 they represent these two groups respectively. 



Some specimens are of interest as showing the nature of the 

 process of deposit of silver in the limestone. A Zaphrentis and 

 an ? Orihis in good preservation, are partially replaced by 

 argentiferous iron, which retains their structual details. This 

 shows clearly that the process is one of replacement of the lime- 

 stone by a fluid holding the metals in solution, and not by injec- 

 tion. This is also demonstrated by the undisturbed condition of 

 the thin bedded limestone where traversed by veins of ore.— E. 

 D. Cope. 



Insects of the Amyzon Shales of Colorado. — In the Bulle- 

 tin of the U. S. Geological Survey of the Territories of Hayden, 

 Mr. Scudder publishes a review of the geology and palaeontol- 

 ogy of the above deposit. He observes: " The insects preserved 

 in the Florissant basin are wonderfully numerous, this single 

 locality having yielded in a single summer more than double the 

 number of specimens which the famous localities at Oeningen, in 

 Bavaria, furnished Heer in thirty years. 



" The examination of the immense series of specimens found 

 at Florissant has not gone far enough to yield data sufficiently 

 definite for generalizations of any value, or which might not be 

 altered, or even reversed, on further study. It may, nevertheless, 

 be interesting to give a running note of what has been observed 

 in assorting the collection, and to make the single comparison 

 with the Oeningen insect fauna which the number of individuals 

 will furnish. 



"This is indicated by the following table, based on a rough 

 count of the Florissant specimens, but which cannot be far 



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