692 STRATIGRAPHICAL GEOLOGY. [Boox VI. _ 
in the Tyrol as far as the south end of the Vienna basin. A few ortho- 
ceratites, brachiopods, and other fossils found in this belt are regarded 
as Upper Silurian forms. Remains of corals, crinoids, and brachiopods 
have been met with even deep beneath the limit formerly drawn between 
the Paleozoic and Archean rocks of the Alps, so that there is now 
reason to believe that a considerable part of the crystalline schists may ~ 
be altered Palzeozoic rocks. Silurian rocks containing graptolites have 
also been met with among the southern slopes of the Alps in Carinthia. 
North America.?—In the United States and Canada Silurian 
rocks spread continuously over a vast territory, from the mouth of 
the St. Lawrence south-westwards into Alabama and westwards by the 
great lakes. ‘They almost encircle and certainly underlie all the later 
Paleozoic deposits of the great interior basin. The rocks are most typically 
developed in the State of New York, where they have been arranged as in» 
the subjoined table: 
IV. Oriskany 
Formation. 
B. Upper Silurian. 
{Oriskany sandstone (Spirifera arenosa) . é .) 

((4) Upper Pentamerus limestone (Pentanerus pseudo- 
rat: Sawer galeatus) . . , - = hts : : 
Helderberg (3) Delthyris limestone (Meristella levis). : ‘ 
Formation, \622 Lower Pentamerus limestone (Pentamerus galeatus)+Ludlow. 
‘{(1) Water-lime (Tentaculites, Eurypterus, and Ptery- 
\ gotus) i 3 ; é - : : . 
Tr) Galea Onondago salt group, consisting of red and grey marls, 
: sandstones and gypsum, with large impregnation of 
common salt, but nearly barren of fossils ; - 
(3) Niagara shale and limestone (Halysites, Favosites, 
Calymene Blumenbachii, Homalonotus delphinoce-}Wenlock. 
phalus, Leptena transversalis, &c.) : : : 
(2) Clinton group (Pentamerus oblongus, Atrypa U 
reticularis, &c.) . : ; ; - ° . Li aa 
(1) Medina group with Oneida conglomerate (Modio- Fi aes 
lopsis orthonota) . : ° . . Dees 
A. Lower Silurian. 
(3) Cincinnati (Hudson River) group (Syringopora, Halysites, 
Diplograptus pristis, Pterinea demissa, Leptena sericea). 
(2) Utica group—Utica shale. 
Formation. 
I. Niagara 
Formation. 
II. Trenton ; ; Graptolithus amplexicaulis 
Formation. fa Trenton limestone. Titnasleds concentata 
is’ (1) Trenton) Black River lime- Orthi ; ete & 
group.) stone, rthis bili Murchi- 
Birdseye limestone. sonia, onularia, Orthoceras, 
\ Cyrtoceras, &e. 
(3) Chazy group—Chazy limestone (Maclurea magna, M. Logani, 
Orthoceras, Illenus, Asaphus). 
(2) Quebec group (upwards of 100 species of trilobites of genera 
Agnostus, Ampyx, Amphion, Conocoryphe, Dikelocephalus, 
Illeanus, Asaphus, &¢., more than 50 species of graptolites). 
(1) Calciferous group (graptolites, Lingulella acuminata, Lep- 
tana, Conocardium, Ophileta compacta, Orthoceras primi- 
genium, 14 species of trilobites of the genera Amphion, 
Bathyurus, Asaphus, Conocoryphe). 
aN formation, representing Cambrian (see ante, 
p. 660). 
I. Canadian 
Formation. 

' Von Hauer, “ Geologie,” p. 216. Stache, Jahrb, Geol. Reichsanstalt. xxiii. p. 175; 
xxiv. 136. The latter memoir contains a detailed description of the greywacke zones of 
the eastern Alps, which the author divides into five pre-triassic groups: I. Quartzphyllite 
group; 2. Kalkphyllite group; 3. Kalkthonphyllite group; 4. Group of the older 
greywackes (Silurian and Devonian); 5. Group of the Upper Coal and Permian rocks. 
* See especially the Memoirs of the Geological Survey of Canada and the numerous 
monographs of Prof. James Hall, of Albany, 

