664 



REPOKT OF NATIONAL MUSEUM, 1904. 



ideas as to flexures and overthrust faults. The order of succession of 

 the strata would then stand as below, that given in the paper of 1S42 

 being introduced for comparison. It will be at once noted, as later 

 charged by Dana (1888), that "the system is for the most part turned 

 the other side up." 



Taconic system, 184% ■ 



6. Stockbridge limestone. 



I a. Magnesian slate of < Jreylock — per- 

 haps a repetition of No. 3. 

 b. Granular quartz. 

 4. Limestone. 



:!. Magnesian slate of Taconic Mountain. 

 2. Sparry limestone. 

 1. Taconic slate. 



Taconic system, Dectonber, IS44. 



6. Black slate, Bald Mountain. 



5. Taconic slate. 



4. Sparry limestone. 



3. Magnesian slate. 



2. Stockbridge limestone. 



1. Granular quartz. 



Fig. 133. — Atops trilineatus. 



The system as here outlined, Emmons argued, occupied a position 

 inferior to the Champlain division of the New York s} 7 stem, or the 

 lower division of the Silurian system of Mr. Murchison. 



The fossils found in 

 the Black slate, it 

 should be mentioned, 

 were Trilobites — 

 Atops trilineatus, a 

 form allied to Triar- 

 thrus beckii and Ell/ip- 

 t<ic< phala asaplu>i< It s, 

 and annelid markings, 

 chiefly those of Neire- 

 ites and Myrianites. These were described by Hall in 1846, and the 

 ground taken that the Atops smd Triarthrus were identical and refer- 

 able to the Hudson River group, the Elliptocephala being referred to 

 the genus Olenus® an Upper Cambrian form. 



At the Boston meeting (1847) of the Association of American Geolo- 

 gists and Naturalists, Prof. C. B. Adams discussed the Taconic rocks 

 of the northern part of Addison County, Vermont, a locality judged 

 to be particularly favorable for study, since the rocks pass here from 

 a highly to but slightly metamorphosed and disturbed condition. He 

 exhibited sections of Snake and Bald mountains and from Lake Cham- 

 plain to the Green Mountains, and thought to show that the Taconic 

 quartz rock was probably the metamorphic equivalent of the red sand- 

 rock (regarded by Adams as belonging to the Champlain division of 

 the New York geologists), and that the Stockbridge limestone was the 

 equivalent of the calcareous rocks overling the red sandrock, rather 

 than that of the lower limestone of the Champlain division. 



a Later, Olenellus of the Lower Cambrian. 



