320 Correlation of the Upper Cretaceous Formations 



no assemblange of forms which can properly be said to constitute a 

 Matawan fauna and another a Monmouth fauna, which are any more 

 distinct in character than the faunas of successive formations. 



" If the foreign Belemnitella element introduced in the Mt. Laurel- 

 Navesink fauna had persisted, and had supplanted in any notable degree 

 the older faunas in the region, instead of being a minor, although impor- 

 tant episode in the faunal history, merely being one element in a fauna 

 which as a whole was closely related to an earlier one, and which was 

 followed by another one in which the Belemnitella element was absent, 

 and which was essentially a recurrence of an earlier fauna, then there 

 would be good paleontological reasons for recognizing the Matawan and 

 Monmouth as distinct major divisions." % 



The initiation of the Monmouth (Mt. Laurel-Navesink) fauna marks 

 the introduction not only of Belemnitella americana, but also of Exogyra 

 costata, Turritella vertebroides and its northern analogue T. paraverte- 

 broides, Anchura pennata, Eutrephoceras dekayi, and probably of Lio- 

 pistha protexta, all of them forms that have served as guide fossils in 

 separating the higher from the lower Upper Cretaceous faunal zone 

 throughout the South Atlantic and Gulf states. These zones are so clearly 

 defined in the south that it has been possible to differentiate them on the 

 Federal Survey maps. While it is true that a number of the Matawan 

 forms persist far into the Monmouth, this does not in the least detract 

 from the significance of the initiation of a new element of more than local 

 importance at the opening of the Monmouth. 



The time of extinction of an old fauna is considered at present as a 

 less significant fact than the time of initiation of a new one, and if that 

 new one be sufficiently virile to characterize the molluscan life from New 

 Jersey south through Georgia and west to Texas, it indicates something 

 more than a minor oscillation in a restricted area and should be given the 

 relatively higher rank which it deserves. 



The Matawan is represented in Maryland and Delaware in two distinct 

 areas, the one along the Chesapeake and Delaware Canal and the other in 



1 Weller, S., Geol. Survey N. J., Paleontology, vol. iv, 1907, pp. 177, 178. 



