178 PROCEEDINGS OF THE AMERICAN ACADEMY 



the scarcity of fossils cannot be explained on the ground that the rocks 

 Lave not been examined. This series of rocks have be(3n under the 

 eyes of geologists since 1817 ; they have been examined minutely m 

 Rensselaer and Washington counties, New York, and Berkshire, Mas- 

 sachusetts, and with more or less care over the whole area of western 

 Vermont. A few fossils only have been discovered over this large 

 area. Of the fossils which these rocks have furnished, marine ve^eta- 

 bles are the most common, but they are limited to a few obscure spe- 

 cies ; the thickness of the bed in which they occur is at least 2,000 fieet. 

 Graptolites rank next in numbers ; they even exceed the marine plants 

 in the number of species which have been found. In addition to the 

 foregoing, there are three species of Trilobites and some four or five 

 of mollusca." 



Dr. Emmons describes four marine plants, twenty-one Graptolites, 

 six Mollusca, and three Trilobites. Of the Mollusca he says, '* Most 

 of the mollusca of this system belong to the family of Brachiopods, 

 all of which are so minute that it is difficult to discover their most im- 

 portant characters." And of the Trilobites he observes, '' The S2)ecies, 

 however, are unknoton in the Silurian period." Finally, Emmons sum- 

 marizes the Taconic system in the following manner. 



"■ The Taconic system rests, then, on the following points : — 



" 1. Its series, divided into groups, are physically unlike the Lower 

 Silurian series. 



" 2. It supports unconformably at numerous places the Lower Silu- 

 rian rocks. 



" 3. It is a vital system, having been deposited during the period 

 when organisms existed. 



" 4. As a natural history system, it is unlike the Lower Silurian ; 

 first, in containing fossils yet unknown in the Lower Silurian ; and, 

 second, in the absence of the typical forms which are prevalent in the 

 Lower Silurian. 



" 0. In the Taconic system we have the palaeozoic and sedimentary 

 bases ; the former comes in far above the latter, or at a long period 

 subsequent to the time when deposits began to be formed. 



" G. The Taconic system carries us back many stages farther in time, 

 when life gave vitality to its waters, than the Silurian. It represents 

 a period vastly longer, though it may occupy a less superficial area." * 



In Chapters X., XL, and XII. of his " Geological Report of the 

 Midland Counties of North Carolina," (Raleigh, 1856, 8vo,) Dr. Eni- 



* American Geology, Part II. The Taconic System, p. 122. 



