CLASSIFICATION AND CORRELATION. 181 



more clastic sediments had been deposited. At a later period of 

 emergence the deeper-water fauna would shift to the southeast 

 and the shallower-water fauna would again occupy the region it 

 had formerly occupied. These conditions furnish a rational ex- 

 planation for the recurrence of the two essential elements in this 

 fauna in New Jersey, as well as for the more or less intimate 

 mingling of the two faunal elements which is observed in certain 

 horizons. Since there could have been no hard and fast line 

 separating the shallower and deeper-water faunas, members of 

 the shallower-water fauna were free to wander into the deeper 

 waters, and the deeper-water forms into the shallower waters, 

 while in the belt of intermediate depth there was of necessity a 

 mingling of the two faunal elements. 



If the conditions here postulated are the true interpretation of 

 the conditions in New Jersey during the existence here of the 

 Ripleyian fauna, the shallower-water formations should, on 

 being traced down the dip, gradually become more glauconitic, 

 and at some distance in this direction the entire series of sediments 

 might be found to be glauconitic in character. On the other 

 hand, the more glauconitic formations as seen under present con- 

 ditions of exposure, must originally have had their shallower- 

 water equivalents characterized by the absence of glauconite and 

 by the shallower-water fauna, which has been entirely removed 

 by erosion since Cretaceous time. 



That the oscillations of the Cretaceous coast across New Jer- 

 sey were but local phenomena is shown in the case of the Red 

 Bank 'formation, which cannot be recognized beyond Monmouth 

 County, a fact indicating that the elevation which brought about 

 the change from Navesink to Red Bank conditions was limited 

 to the northeastern portion of the area, while farther southwest 

 the deeper waters continued with the accompanying- glauconitic 

 deposits. In this more southwestern region the depression accom- 

 panying the Navesink marl of eastern Monmouth County was not 

 so marked since the more clastic Mount Laurel sand, apparently 

 a shallower-water formation, was, in part at least, contempo- 

 raneous with it. 



In tracing these elements of the Ripleyian fauna beyond the 

 limits of New Jersey the local details in their history will not 



