446 FOSSILS. 



Chcetetes, Stromatopora, Zaphrentis, and one shell, resembling Euomphalus. There are 

 at least two species of encrinites. No fossils have been found in this limestone elsewhere. 



The magnesian slate, or rather a bed of limestone belonging to the series, presents us 

 with an obscure disciform shell, and a few encrinal remains. 



In the upper part of the system, fossils are more abundant. There are numerous 

 graptolites, Lingulce, and Oboli, and three genera of trilobites. In Vermont there are 

 fucoids, graptolites, annelid trails, and four trilobites in this division. Those which 

 have been named are the Grraptolithus Milesi, Barrandia Thompsons, B. Vermontana, and 

 Bathynotus holopyga. Prof. Emmons regards all the trilobites as Paradoxides, and two of 

 them he names P. brachycephalus, and P (?) quadrispinous. Still another trilobite in Ver- 

 mont, is the Atops punctatus of Prof. Emmons. 



^RESUMPTIONS IN FAVOK OF THE TACONIC SYSTEM. 



1. Its similarity to the Cambrian System in Europe. The rocks in Europe, particularly 

 on the British Islands, are abundantly fossiliferous and rarely metamorphic as far as the 

 base of the lower Silurian. In the Cambrian, the rocks exhibit traces of metamorphic 

 action, but not enough to obscure organic remains, of which but few relics are found. 

 Below the Cambrian are the metamorphic hypozoic rocks. The correspondence of the 

 lower Silurian, Taconic and Lauren tian rocks of America, to the lower Silurian, Cambrian 

 and hypozoic of England is perfect. But on the contrary supposition, that the Taconic 

 system exists in America only in imagination, then we have no similarity between the 

 corresponding American and European strata. The thickness of the Cambrian in Wales 

 and the Taconic in New York and Vermont corresponds. 2. Therefore, we have a presump- 

 tion that the old doctrine of the Laurentian age of the New England azoic rocks is cor- 

 rect. The doctrine of metamorphism as advocated by many authors becomes extravagant. 

 How much more in accordance with the analogies of European strata to suppose that the 

 chief locality of the action of metamorphism was in the Laurentian period, and that cases 

 of subsequent thorough alteration are exceptional! The theories of the Laurentian age 

 of the azoic rocks of New England, and the Cambrian age of the Taconic system, stand 

 or fall together. 



3. The Taconic Bocks are physically unlike the lower Silurian. There is a general corres- 

 pondence in the kinds and order of rocks in the two systems, namely, a sandstone, a 

 limestone and a slate. But the granular quartz is totally unlike the Potsdam sandstone, 

 the marbles and limestones are unlike the lower Silurian limestones. All the marble 

 of the lower Silurian rocks is in the Black River limestone twelve feet thick. This is 

 near the middle of the limestones. The Stockbridge marbles in Vermont are near the 

 top of the limestones, and are more than a hundred feet thick. There is nothing like the 

 magnesian slates in the Hudson River group. 



4. The Taconic System underlies the lower Silurian. It would be a waste of time to dwell 

 upon this argument, as its points have already been stated. It is completely convincing 

 by itself. 



5. The thickness of the Taconic and lower Silurian Bocks do not agree. The lower Silurian 

 rocks in Vermont cannot be 2,000 feet thick. The Taconic rocks cannot be less than 

 25,000 feet thick. The maximum of the Hudson River group in Pennsylvania is 6,000 



