88 



CRETACEOUS PALEONTOLOGY. 



chantville or which reappear in the Mount Laurel-Navesink 

 fauna without being present in the intervening Woodbury below 

 or Wenonah above. 



The most conspicuous characteristic in the Marshalltown fauna 

 is a new element, which has not been present in any of the earlier 

 faunas in this region and which may represent a new immigra- 

 tion into the Cretaceous area of New Jersey at this time, an 

 element which persists in the recurrent Cucullaea faunas of later 

 formations, and which has its most typical manifestation in the 

 Mount Laurel-Navesink fauna. This element is represented 

 most conspicuously by the ponderous species of Exogyra and 

 Gryphaea, by the little oyster O. falcata which is of the type of 

 0. larva, and by Gryphaeostrea vomer. In the Cliffwood, Mer- 

 chantville and Woodbury formations these oyster-like shells are 

 essentially absent. An occasional example of the internal cast 

 of an Hxogym, much smaller than the usual full-grown repre- 

 sentatives of this genus in the Marshalltown and Navesink 

 faunas, occurs in the Merchantville, but no suggestion of the 

 genus has been met with in the Woodbury. No examples at all 

 of Gryphaea and Gryphaeostrea have been met with in these lower 

 faunas, and only the merest suggestion of oysters of the type of 

 O. larva. In strong contrast with the paucity of these forms in 

 the faunas of the Cliffwood, Merchantville and Woodbury, their 

 great abundance in the Marshalltown is a most striking char- 

 acteristic of the fauna. The species of these shells are for the 

 most part different from those of the same types in the Mount 

 Laurel-Navesink fauna, Exogyra ponderosa, Gryphaea mutabilis 



