GREY SANDSTONE OF OSWEGO. 67 



ville and above the village. In that section there are some fossils which are more numerous 

 there ihan in other sections, and usually associated together, such as the Semioval stropho- 

 mena and the Tortoise orthis. These fossils, and a few others, were also found in a similar 

 rock on the Hudson river, to the south of Newburgh, evidently there forming the upper part 

 of the Hudson river group. 



Carbonate of lime appears to be rather more abundant in the range of the upper division 

 in Oswego, than in the other counties ; thus at Pulaski near the water line, there is a layer 

 highly charged, of about ten inches in thickness. 



In the collection of the Academy of Natural Sciences at Philadelphia, there is a specimen 

 of this rock, picked up on the south shore of Lake Erie, which is of interest, from its showing 

 whence it was transported, and from its goodness as a limestone, being purer than any of the 

 kind found in the third district. Its origin is shown by its enveloped fossils, and the olive- 

 colored sandstone which adheres to one of its sides. 



The two divisions exist separately in Pennsylvania ; the' lower one ranges to the east of the 

 Blue mountains in the Kittatinny valley, and is worked for roofing slate on both sides of the 

 Delaware river. The other division, having the same characters in all respects as in New- 

 York, occurs on the edge of Nippenose valley, near the west branch of the Susquehannah, 



In Ohio and Indiana, the upper division, with its fossils, "exists : the lower one has not yet 

 been observed. It is there highly calcareous, and forms the upper part of the blue limestone 

 of these two States. In those States, the whole, from the Trenton limestone to the sandstone 

 shale of Pulaski, consists of but one rock or mass, according to western observers ; a fact 

 which, when well established, will be of importance in the grouping of the elementary divi- 

 sions of the New-York system. 



7. GREY SANDSTONE OF OSWEGO. 

 (No. 4. Pennsylvania Survey.) 



This rock consists of grey sandstone with a greenisli tint, and of dark blue and greenish 

 shale. It is distinguished from the sandstone shale of Pulaski, by the absence of its fossils, 

 and by its connection with the red sandstone, these two masses interlocking with each other : 

 the lower part of the latter mass is non-fossiliferous, and the upper part contains fossils 

 wholly different from those of the Pulaski rock. 



This sandstone is the next mass to the sandstone shale of Pulaski, resting upon and bor- 

 dering it to the west and south in the third district. The sandstone is not in very thick or 

 regular layers, and it contains but little shale. The color generally is grey, with a greenish 



