12 CRETACEOUS GROUP | 
sons I have hitherto been able to make, the same species 
of fossils are found throughout: thus the Ammonites pla- 
centa, Baculttes ovatus, Gryphxa vomer, Gryphxa muta- 
bilis, Ostrea falcata &c., 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. Mantell, 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 3 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, Turritelle, and other Tertiary genera.” 
* Journ. Acad. Nat. Sci. of Philad. Vol. VI. p. 97. 
