16 CRETACEOUS GROUP 
pebbles, in fact a siliceous gravel, cemented by green 
phosphate and brown oxide of iron, and embracing a 
vast quantity of the usual marl fossils, especially Gry- 
phea, Exogyra and Belemnites: the former two, how- 
ever, are usually so charged with iron as greatly to im- 
pair their characters, and the Belemnites are either more 
or less decomposed, or replaced by crystallized phos- 
phate of iron. The gravel is not superficial, but may be 
observed to a depth of many feet. 
As this gravel forms an exception to ordinary appear- 
ances, it at first occurred to me that it might have been 
derived from a partial mixture on the surface of diluvial 
debris.* An instance of this kind occurs on Mr. For- 
syth’s land, near Pemberton, where the diluvial gravel 
has torn up the marl, and the two are mingled together 5 
and among the characteristic constituents of the former, 
were found several masses of anthracite coal, of which 
there is no locality short of an hundred miles. 
Calcareous Strata. ‘The calcareous beds have been 
traced as far south as Salem, and north to Vincentown, a 
tract nearly sixty miles in length, in a direction nearly 
parallel to the Delaware river, and from seven to ten 
miles east of it. ‘These beds are marked throughout by 
the several varieties of calcareous rock already described, 
(p. 10,) and characterized by abundance of Zoophytes, 
Echini, and a few species of shells. These fossils, with 
* Should the gravel be hereafter found to form an integral part of these beds, it 
will be no anomaly in this formation, for the same phenomenon occurs in the lower 
green sand strata in England.—Coneyb. and Phil. Geol. p. 137. 
