Parr IL. Seer. iii. (1) §2.] DEVONIAN. 705 
geological interest in the union which it contains of the same two 
distinct petrographical and biological types found in Europe. Traced 
along the Alleghany chain through Pennsylvania into New York, the 
Devonian rocks are found to contain a characteristic suite of marine 
organisms comparable with those of the Devonian system of Europe. 
But on the eastern side of the great range of Silurian hills in the north- 
eastern States, we encounter in New -Brunswick and Nova Scotia a 
succession of red and yellow sandstones, limestones, and shales nearly 
devoid of marine organisms, yet full of land-plants, and with occasional 
_ traces of fish remains. 
The marine or Devonian type has been grouped in the following 
_ subdivisions by the geologists of New York: 
Catskill Red Sandstone. 
Chemung group. 
Portage group. 
Genesee group. 
Hamilton group. 
(Marcellus group. 
ae (Corniferous or Upper Helderberg group. 
Lower DEyontan’ .4Schoharie Grit. 
\Cauda-galli Grit. 
Upper DEVONIAN .4¢ 
In the Lower Devonian series traces of terrestrial plants (Pstlophyton, 
Caulopteris, é&c.) have been detected, even as far west as Ohio. Corals 
(cyathophylloid forms, with Favosites, Syringopora, &c.) abound, especially 
in the Corniferous Limestone, perhaps the most remarkable mass of coral- 
rock in the American Paleozoic series, and from which Hall has made a 
magnificent collection of specimens. Among the brachiopods are species 
of Pentamerus, Stricklandinia, Rhynchonella, and others, with the charac- 
teristic Huropean form Spirifera cultrijugata, and the world-wide Atrypa 
reticularis. ‘The trilobites include the genera Dalmanites, Proétus, and 
Phacops. The earliest known traces of American fishes occur in the 
_Corniferous group. They consist of ichthyodorulites, and teeth of 
cestraciont and hybodont placoids, and plates, bones, and teeth of some 
peculiar ganoids (Macropetalichthys, Onychodus). 
In the Hamilton formation (embracing the Marcellus shale, the 
Hamilton beds, and the Genesee shale) remains of land-plants occur, but 
much less abundantly than among the rocks of New Brunswick. 
Brachiopods are especially abundant among the sandy beds in the centre 
of the formation. ‘They comprise, as in Hurope, many broad-winged 
spirifers CS. mucronatus, &c.), with species of Productus, Chonetes, Athyris, 
_&c. The earliest American goniatites have been noticed in these beds. 
Newberry has described a gigantic fish (Dinichthys) from the Black Shale 
of Ohio. : 
The Portage and Chemung groups have yielded land-plants and 
fucoids, also some crinoids, numerous broad-winged spirifers, with 
Aviculz, and a few other lamellibranchs. These strata in the New York 
region consist of shales and laminated sandstones, which attain a 
maximum thickness there of upwards of 2000 feet, but die out entirely 
towards the interior. ‘They are covered by a mass of red sandstones and 
conglomerates—the Catskill group, which is 2000 or 3000 feet deep in the 
Catskill Mountains, and thickens along the Appalachian region to 5000 or 
6000 feet. Those red arenaceous rocks bear a striking similarity in their 
lithological and biological characters to the Old Red Sandstone of Europe. 
2 Z 
