44 CRETACEOUS PALEONTOLOGY. 



author has considered these clays as a distinct formation equiv- 

 alent to the Magothy formation in Maryland 1 . These Cliffwood 

 clays, with their associated sand and lignite, are clearly distinct 

 from the Merchantville as has already been pointed out, both 

 faunally and lithologically, and there is no great difficulty in 

 tracing the basal line of the Merchantville even where the sub- 

 jacent Magothy beds are argillaceous. 



The transition from the Merchantville to the Woodbury above 

 is less sharp than that between this formation and the subjacent 

 one, but it is usually accomplished within a thickness of from 

 one to three feet. 



The thickness of the Merchantville clay-marl increases some- 

 what from northeast to southwest. In Monmouth County its 

 thickness is about 35 feet, at Bordentown it is 60 feet, and in 

 Salem County about the same. 



FAUNAS OF THE MERCHANTVILLE CLAY-MARL. 



The Merchantville clay-marl is usually fossiliferous where it 

 is well exposed, especially the more glauconitic beds of the for- 

 mation. More or less complete collections have been made from 

 the formation at eight different localities along the belt of outcrop 

 from Monmouth County near Raritan Bay to Merchantville in 

 Camden County, a distance of about 60 miles. Through this 

 entire extent the fauna retains its integrity in its more essential 

 characteristics, and judging from collections in the Philadelphia 

 Academy of Science the integrity of the fauna persists at least 

 as far as the deep cut on the Delaware and Chesapeake canal in 

 the State of Delaware, a further distance of 45 miles. In New 

 Jersey, so far as it has been observed, the fauna is purer in the 

 more northeastern localities from which it has been studied, the 

 mingling of the species more characteristic of the Woodbury 

 clay fauna being more noticeable to the southwest. 



The eight local faunas of the formation which have been 

 studied will be recorded in order, beginning with the more north- 

 eastern ones. 



1 Am. Jour. Sci., 4th Ser., vol. 18, p. 440. 



