252 Prof. Rogers's Address before the 



full and satisfactory. Perhaps no one group of rocks in North Ameri- 

 ca covers so many square miles, or more abounds in various, expres- 

 sive and beautifully preserved remains of former life, than our green- 

 sands and cretaceous limestones. Commencing on the northeast at the 

 Raritan Bay, these deposits range in a contracting belt along the Atlan- 

 tic plain through New Jersey into Delaware. There they disappear be- 

 neath the tertiary, and though not visible in Maryland, Virginia or North 

 Carolina north of Cape Hatteras, they probably form the floor of the 

 tertiary in all this space ; for in North Carolina they emerge again, and 

 hold the same relations to the older and newer systems of strata which 

 they observe in New Jersey. From the Cape Fear river these cretace- 

 ous deposits spread southwestward, occupying the seaboard of South Car- 

 olina, much of the southern half of Georgia, a large part of Florida, 

 the southern half of Alabama, and the chief part of Mississippi ; and 

 west of the great river of that name, they expand so as to underlie 

 the surface of a great portion of the enormous interior basin of the 

 continent from Louisiana and Texas northward to the upper Missouri, 

 and westward probably to the Rocky Mountains. Throughout all the 

 southern tracts, they support detached local patches of interesting ter- 

 tiary formations, principally eocene. 



This whole cretaceous group of the United States is viewed by Dr. 

 Morton and Mr. Conrad, after a careful investigation of the fossils, to 

 consist of three great divisions, called the upper, middle and lower.* 

 The upper division includes the nummulite limestone, familiarly called 

 the " rotten limestone" of southern Alabama and the contiguous south- 

 ern states. The middle division consists of a thin but very fossiliferous 

 straw-colored limestone, capping in small patches the greensand beds of 

 New Jersey, and this is supposed by Dr. Morton to be contemporaneous 

 with the European white chalk. The lower division embraces the ex- 

 panded greensand deposits of the Atlantic states and the Missouri basin, 

 and this is considered by Dr. Morton and others to have been formed 

 contemporaneously with the strata which in Europe lie between the 

 chalk and the oolites. 



Above the middle division or thin limestone of New Jersey, there 

 occur in that state two strata not mentioned in Dr. Morton's classifica- 

 tion, the lowest a yellow ferruginous sand with fossils, and the upper- 

 most a coarse brown ferruginous sandstone. As many of the fossils of 



* See a tabular view of organic remains of the cretaceous strata, by Dr. Morton, 

 in the Journal of the Acad. Nat. Scien. of Phila., vol. viii, part 2. 



