94 * Marl of New Jersey. 
sent Mr. M. a small series of the organic remains of the marl dis- 
trict, &c. upon which he makes an interesting commentary, and then 
adds— I have read your papers on the green sand of America, 
(in the Journal of Science) with great pleasure and interest; and I 
entirely agree in the opinion you express, that the strata in question, 
bear a decided analogy to the inferior division of the chalk formation 
of Europe. Your limestone above green sand, reminds me very 
much of the Maestricht beds. The latter 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 be- 
tween the so ealled secondary and tertiary formations, I believe it 
will ultimately be found, that this is not the natural order, but the ex- 
ception ; 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. So also I believe we shall find that even the 
tertiary formations rur insensibly into the modern deposits.” 
I had some years ago, and indeed in my first* paper on this sub- 
ject, mentioned some resemblances which appeared to me to exist 
between the Maestricht beds and the green sand of New Jersey ; but 
Mr. Mantell’s suggestion that such analogy obtains between the lime- 
stone superimposed on our marls, and the Maestricht deposits, is new 
to me, and seems to be founded in fact. The limestone in question,- 
is apparently more recent than the green sand, and has hitherto afford- 
ed fewer pelagic, and more littoral fossils. It has been examined 
as you know, in numerous quarries between Salem and Vincentown, 
in New Jersey; (a distance of about forty miles) but has not yielded 
any multilocular univalve, unless the equivocal fossil which I have 
named Belemnites ambiguus, be of this character. Its characteris- 
tic relics, as I have elsewhere mentioned, are scalariz, varieties of 
Gryphea convexa, and G. vomer, with numerous Linnean madrepores 
and echini. Is this a connecting link between our secondary and 
tertiary beds? My friend Mr. Nuttall has recently detected the 
green sand near Cahawba, in Alabama; establishing the known ex- 
tent of this formation to a distance of about a thousand miles; for at 
Cahawba, the Exogyra costata, Ostrea falcata, and other species of 
shells, are specifically identical with those from New Jersey; nor 
indeed is there the shadow of a difference between them. Dr. Wm. 
Blanding has communicated some very interesting facts respecting 
* Jour. Acad. Nat. Sciences, Vol. vi. p. 97. 
