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and fossils which characterize it at Sandy Creek, the typical locality 

 of Jefferson county, in the State of New York. 



Utica Slate. — The only locality where I met with these strata was 

 on the shore of Lake Champlain, a short distance behind the hotel of 

 Highgate-Spriugs. The thickness of what is not covered by the water 

 is forty feet ; they have been overturned, and lie below the Trenton 

 Limestone. Dr. G. M. Hall, of Swanton, has found this group on 

 several of the islands in the middle of the lake. 



Trenton Limestone. — This group, with its usual characters, is found 

 at Highgate- Springs. 



Black River Group. — Comprising the Blach River limestone, Birds- 

 eye limestone, and Chazy limestone. It is common to find now and 

 then, scattered along the whole line from Highgate-Springs to Bridge- 

 port, in small patches, lying in discordant stratification over the difierent 

 divisions of the upper Taconic, some beds of limestone of this group. 

 The thickness seldom reaches forty feet. They contain numerous 

 fossils characteristic of the group. Localities : Highgate-Springs, West 

 Georgia (near Mr. Parker's house), and Snake Mountain. At High- 

 gate-Springs the last bed of the Black River group is formed of a hard, 

 blue, grayish limestone, two feet thick, with Ampyx Halli, very fossilife- 

 rous, and constituting a very conspicuous and easy point de repere. 



Calciferous Sandrock. — Until lately this group was not considered 

 of the importance that it really is, and it is due mainly to the researches 

 of Mr. Billings, of Montreal, that we have at last come to a true knowl- 

 edge and understanding of its characters, and the great place it occu- 

 pies in the Lower Silurian, In fact, the Calciferous Sandrock is the 

 base of the Lower Silurian, and contains half the thickness of the beds 

 composing the Lower Silurian of North America. In the Paleontol- 

 ogy of New York, by James Hall, Vol. i., thirteen or fourteen fossils 

 are described as being the only remains of organized beings found in 

 the Calciferous Sandstone, whereas now Messrs. Jewett Billings, G. M. 

 Hall, Perry, Farnsworth, J. Richardson, J. Bell, and myself, have 

 succeeded in collecting from this group in Vermont, New York, Canada, 

 and at Belle Isle (Newfoundland), more fossils than in all the other 

 Lower Silurian groups put together, — that is to say, about twelve 

 hundred species, of which one hundred are new Trilobites. To any 

 one, however, acquainted with the diSerent Silurian faunre of Europe, 

 it was evident that the second fauna of North America had not been 

 well worked out by the Paleontologist of New York, and that at least 

 a good half of it had escaped his hasty and superficial researches in 

 the field ; so that this discovery of numerous fossils belonging to the 

 second fauna in the Calciferous Sandstone, however sudden it might 

 be, was not unexpected to any one who has studied the different 

 memoirs of Barrande on the subject. 



