J. D. Dana on American Geological History. 315 
York beds of this rock had afforded only a few mollusks; but 
the investigations of Owen and others have added the re remaining 
tribes; and this diversity of forms is confirmed by Barrande in 
Bohemian researches. 
Among the genera, while the most of them were ancient forms 
that afterwards hecame extinct, and through succeeding ages 
shell had ‘the anomalous chemical constitution of bones, se 
mainly phosphate of lime; — afterwards he found in a modern 
Lingula 
the very same com: sition,—a further announcement 
ee acy between the saree and latest events in geolog- 
r 
This “ars sandstone,—called in New York the Potsdam 
sandston the associated Calciferous sand-rock, mar 
the First. Period of the Molluscan Age,—the Porsp ait PERIOD, 
as it may be called.t 
ext fSiowed the TreNTON PERIoD,—a period of limestones, 
(the Trenton limestone among them,) equal to the earlier beds 
‘In geographical limits, and far more abundant in life, for some 
beds are literally she lls and corals packed dow \ in bulk; 
the species were new to the period, the former life having passed 
OM a Geological Ree and 
the Northery part of Iowa, Washin ington Boni acament Tis p. 14, res gales: 
sg in his quarto Report on Wisconsin, f 1852. fossils he mentions 
ong neon a d th 
_ Prof. W f this Jour p? 296), announced the 
ascovery oft the rilobite ® Papani Harlani of Green SE cama! of pearines ) 
in slates ten miles south of Bost on, Mass., a species s found s rrande in his proto- 
wo or cree fossiliferous rock of Bohemia,—thus addin 
ime " ounces also (Meeting 
large Cya aitiophy ilo’ aay in 
The exact age of the rock however 
1 Through th the ¢ i it is now well known that the “ Lower 
Limesto of the ned and a a sandstone with which it — corres- 
“pond to the “erent sandrock of New York. 
c 
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