136 CRETACEOUS PALEONTOLOGY. 



element of the Mount Laurel-Navesink fauna, Belemnitella 

 americana and Terebratella plicata, are restricted absolutely to 

 this horizon in New Jersey, and the zone through which they 

 occur undoubtedly represents a strict zone of contemporaneity 

 through the Cretaceous sediments of the State. This contem- 

 poraneous life zone, however, does not conform strictly with 

 the stratigraphic relations of the sediments, since the Belemnitella 

 fauna occurs in both the Mount Laurel sand and the Navesink 

 marl. The stratigraphic line between these two formations cuts 

 diagonally across the life zone from near its lower limit in the 

 northeast to its summit in the southwest. The fauna of this life 

 zone, in its entirety, is a composite assemblage of life having at 

 least three distinct elements: (i) the indigenous, shifting, Cu- 

 cullaea element recurrent from the Merchantville and the Mar- 

 shalltown; (2) the southern Exogyra element, recurrent from 

 the Marshalltown, and (3) the foreign Belemnitella element, 

 probably an immigrant from Europe. 



