12 CRETACEOUS GROUP 



sons I have hitherto been able to make, the same species 

 of fossils are found throughout : thus the Ammonites pla- 

 centa, Baculites ovatus, Gryphsea vomer, Gryphxa muta- 

 bilis, Ostrea falcata fyc, are found without a shadow of 

 difference, from New Jersey to Louisiana: although some 

 species have been found in the latter state that have not 

 been noticed in the former, and vice versa. 



Again, the calcareous strata appear to be much less 

 extensively distributed than the friable marls, and present 

 considerable difference in their organic characters, as will 

 be noticed in detail hereafter. Again, they appear to 

 form, in all instances, the superior or overlying beds of 

 this formation. 



In my first paper on this subject I mentioned some 

 geological resemblance between the marl of New Jersey 

 and the strata of the celebrated plateau of Maestricht, on 

 the Rhine.* My friend Mr. Man tell, however, to whom 

 I have sent specimens, points out a yet stronger analogy 

 between our calcareous strata and the Maestricht beds. 

 " The latter," he observes, " appear to form, as it were, 

 a connecting link between the chalk and the tertiary, for 

 although, in England, France and elsewhere, there is a 

 marked separation between the so called secondary and 

 tertiary formations, I believe it will ultimately be found 

 that this is not the natural order, but the exception ; and 

 that the transition from one to the other was gradual. In 

 the Maestricht beds we have the Ammonites, Baculites, 

 Echini &c, so characteristic of the chalk, associated with 

 Volutes, Turritella*, and other Tertiary genera." 



■ Journ. lead. N;it. Sci. ofPhilad. Vol. VI. p !»" 



