476 ADDRESS OF T. STERRY HUNT. 
(including the Welsh roofing-slates beneath) amount to eight thou- 
sand feet additional. Recent researches show that these lower 
rocks in Wales contain an abundant fauna, extending downward 
some 2800 feet from the Menevian to the very base of strata re- 
garded as the representatives of the Harlech grits. The brachio- 
poda of the Harlech beds appear identical with those of the Men- 
evian, but new species of Conocephalites, Microdiscus and Parda- 
doxides are met with, besides a new genus, Plutonia, allied to the 
last mentioned. Mr. Hicks, to whom we owe these discoveries,* 
remarks, that the Menevian gives us, for the present, a well 
marked paleontological horizon for the summit of the Cambrian, 
corresponding with the Lower Cambrian as defined by Sedgwick. 
The Upper Cambrian in North America would thus include the 
lower half of the Champlain division from the base of the Potsdam 
to the summit of the Levis (including perhaps the Chazy), while 
the Lower Cambrian, (the Cambrian of Murchison and Hicks) is 
represented by the strata holding Paradoxides in Newfoundland, 
New Brunswick and eastern Massachusetts. Although no strata 
marked by these fossils have yet been found in the Appalachians, 
it is not improbable that such may yet be met with. In May, 
1861, I called attention to the fact that beds of quartzose con- 
glomerate at the base of the Potsdam in Hemmingford, near the 
outlet of Lake Champlain on its western side, contain fragments 
of green and black slates, “showing the existence of argillaceous 
slates before the deposition of the Potsdam sandstone.” f The 
more ancient strata, which furnished these slaty fragments to 
the Potsdam conglomerate, have perhaps been destroyed, or arè 
concealed, but they or their equivalents may yet be discovered 
in some part of the great Appalachian region. They should 
not, however, be called Taconic, but receive the prior designation 
' Cambrian, unless, indeed, it shall appear that the source of 
these slate fragments was the more argillaceous beds of the still 
older Huronian schists. Emmons regarded his Taconic system 
as the equivalent of the Lower Cambrian of Sedgwick, but when 
in 1842, Murchison announced that the name of Cambrian had 
ceased to have any zoological significance, being identical with 
Lower Silurian,t Emmons, conceiving, as he tells us, that 
* Geol. Mag., V, 306; and Rep. Brit. Assoc., 1868, p.69; also Harkness and Hicks iA 
Nature, Proc. Geol. Soc., May 10, 1871. 
t Amer. Jour. Sci., II, xxxi, 404, 
t Proe. Geol. Soc., London, III, 642. 
