17 



In the. belt in Virginia, toward the Potomac River, Prof. Rogers 

 had lately found immense numbers of the same Posidonice and 

 Cypridse, crowded together in fine argillaceous shales, and at 

 several points he had met, in the more sandy rocks, vegetable 

 impressions, which, although obscure, are strongly suggestive of 

 the leaves of Zamites. 



In the same belt in Pennsylvania, in the vicinity of Phenix- 

 ville, early last spring, Prof. H. D. Rogers discovered Posidonise 

 in great numbers in a fissile black slate, and on subsequent exa- 

 mination, the same beds were found to contain layers crowded 

 with the casts of Cypridse. Along with these are multitudes of 

 Coprolites, apparently Saurian, resembling in size and form the 

 Coprolites found in the carbonaceous beds on Deep River, and 

 also some imperfect impressions of Zamites leaves. These facts 

 Prof. Rogers considers sufficient to identify, as one formation, the 

 disconnected tracts of this belt in North Carolina and Virginia, 

 and the great, prolonged area" of the so-called New Red Sand- 

 stone of Maryland, Pennsylvania, and New Jersey. 



As to the geological date of this belt, Prof. Rogers said, that 

 the discovery at various and remote points of its course of Posi- 

 donise, Cypridse, and Zamites, most or all of which are identical 

 with these forms in the eastern middle secondary areas of Vir- 

 ginia and North Carolina, makes it extremely probable that these 

 rocks, formerly referred to the New Red Sandstone, and of late 

 more specially to the Trias, are of Jurassic date, and but little 

 anterior to that of the Coal Rocks of Eastern Virginia. 



Prof. Rogers considered the frequent occurrence of Cypridoe 

 in all these belts as a strong evidence of their Jurassic age. While 

 only a few species of Cypridse, and many of the. allied genus 

 Cytherina occur in the Silurian and Carboniferous rocks, there 

 is a total absence of these crustacean remains throughout the 

 series of deposits extending from the base of the Permian to 

 the lower limits of the Oolite. But on entering the latter, the 

 Cypridse re-appear, and become very abundant there, there being 

 no less than twelve species known to belong to the Oolite forma- 

 tions of Europe. 



On comparing the silicified wood, found in the western and 

 eastern belts, Prof. Rogers had found its structure to be the 



PROCEEDINGS B. S. N. H. VOL. V. 2 OCTOBER, 1854. 



