QF THE NEW RED SANDSTONE FORMATION OF PENNSYLVANIA. 195 



the Dreissena of Vanbeneden, {D.pohjmorpha,) which inhabits the Volga and other 

 rivers of the north of Europe, and which has been transferred to, and diffused 

 throughout Great Britain. 



Professor Ansted states that " the whole of the upper new red sandstone of England 

 bears evident marks of its marine origin, even if the occurrence of so large a quantity 

 of salt associated with it, did not place the matter beyond a doub-t. The almost total 

 absence of fossils is, however, a very remarkable phenomenon, and one which is not 

 satisfactorily accounted for, either by the prevailing sandy character of the deposit, 

 or by the quantity of oxide of iron distributed through it." 



The diifusion of salt mentioned here, and which is also well known to prevail 

 throughout the formation in England, and on the Continent, is totally absent in the 

 iVew Red Sandstone of this country, and in this character they altogether differ from 

 each other. The salines of the United States are in the older palaeozoic rocks, having 

 their origin below the carboniferous series, but sometimes passing through the coal 

 rocks to the surface, from the Silurian strata below.* 



In May, of last year, I visited the locality of Upper Milford, in the hope of finding 

 some other portions of the Clepsysaurus, or the remains of other animals in this 

 locality. A diligent search was made, with the assistance of Dr. Shelley and 

 another person, but we were not able to detect the smallest indication of further 

 specimens. One of the principal objects of my visit was to ascertain clearly the 

 position of the rocks from which the bones, in possession of the Academy, were 

 exhumed. The spot, pointed out to me by Dr. Shelley, was at the point of a hill, in 

 the excavation of which, for a road, the rocks were blasted, leaving a perpendicular 

 wall of the confused calcarious conglomerate rock, which was here composed of small 

 portions, cemented by a reddish or greyish, somewhat argillacious, paste, presenting 

 the appearance of masseration, while in other localities the same rock has quite a 

 brecciated and beautiful structure. This locality is near to the north-western 

 boundary of this New Red Sandstone formation; and, in an early part of this paper, 

 I have traced it to the South-west, across the Schuylkill, Susquehanna, and Potomac 

 rivers. 



In the present state of our knowledge of this calcarious portion of the red sandstone 

 deposit of the United States, it is exceedingly difficult to come to a satisfactory 

 conclusion as to its exact equivalent in Europe. On the whole, I am inclined to 

 place it among the superior strata of the Permian system. I do not see any portion 

 of the Magnesian Limestones, which present characters more analogous to ours than 

 the ^^ Brecciated and Pseudo-brecciated Limestones ^^ of Mr. King's "Monograph of 



* The Onondago Salt group gives origin to all the productive salines of New York. It constitutes No. 12 of the 

 New York Survey: is part of No. 5 of the Pennsylvania survey, and forms the middleportionof the Upper Silurian 

 of English geologists. 



