on the Taconic System, 107 



views were given in detail in 1842 in his final report on that 

 part of the State confided to his charge, and in a more special 

 manner in another work entitled " The Taconic System," pub- 

 lished in 1844. In this latter work he figured several species of 

 fossils which had been collected in diff"erent parts of the forma- 

 tion. Two of these were trilobites, and were described under 

 the names of Atops trilineatus and Elliptocephala asaphoides* 

 The others were graptolites, fucoids and apparently trails of anne- 

 lides ; he considered all the species to be distinct from any that 

 had been found in American rocks of undoubted Silurian age. 

 The pre-silurian age of the formation has also been maintained 

 by him in several more recent publications such as his " Ameri- 

 can Geology " — the several repoiis on the geological survey of 

 North Carolina and in his "Manual of Geology." 



On the other hand, Professor Hall placed the whole region in 

 the Hudson River group. In the first volume of the Palaeontol- 

 ogy of New York he identifies Atops trilineatus with Triarthrus 

 Beckii, the characteristic trilobite of the Utica slate ; — Ellipto- 

 cephala asaphoides he refers to the genus Olenus, and describes as 

 congeneric therewith, another trilobite {0. undulostriatus) said to 

 be from the true Hudson River shales. It is scarcely necessary 

 to state that these identifications have always afibrded an ex- 

 tremely powerful objection against the correctness of the position 

 assumed by Emmons, because no species of trilobite is known to 

 range from the Primordial zone up to the top of the Lower Si- 

 lurian. Hall's first volume was published in 1847 and as it is 

 unquestionably the most important work on the Lower Silurian 

 fossils of North America it has been very generally accepted 

 by our physical geologists as a guide. It is not surprising there- 

 fore, that in all the discussions that have taken place during the 

 last fourteen years upon the age of these rocks, the majority of 

 those who did not profess to be naturalists should have arranged 

 themselves on the side of the leading palaeontologist of the 

 country. 



The formation was traced from New York through Vermont, 

 and there identified by Prof. Adams, the State Geologist, with 

 the Hudson River group. The Canadian Surveyors continued 

 it with great labor through a mountainous and partially unin- 

 habited country for nearly five hundred miles further, from the 

 northern extremity of Vermont to the neighborhood of Quebec, 

 and thence along the south side of the St. Lawrence to the mouth 



