[Footnote 9:  The Depths of the Sea, p. 484.]

Professor Duncan finds “several corals from the coast of Portugal more nearly allied to chalk forms than to any others.”

The Stalked Crinoids or Feather Stars, so abundant in ancient times, are now exclusively confined to the deep sea, and the late explorations have yielded forms of old affinity, the existence of which has hitherto been unsuspected.  The general character of the group of star fishes imbedded in the white chalk is almost the same as in the modern Fauna of the deep Atlantic.  The sea urchins of the deep sea, while none of them are specifically identical with any chalk form, belong to the same general groups, and some closely approach extinct cretaceous genera.

Taking these facts in conjunction with the positive evidence of the existence, during the Cretaceous epoch, of a deep ocean where now lies the dry land of central and southern Europe, northern Africa, and western and southern Asia; and of the gradual diminution of this ocean during the older tertiary epoch, until it is represented at the present day by such teacupfuls as the Caspian, the Black Sea, and the Mediterranean; the supposition of Dr. Thomson and Dr. Carpenter that what is now the deep Atlantic, was the deep Atlantic (though merged in a vast easterly extension) in the Cretaceous epoch, and that the Globigerina mud has been accumulating there from that time to this, seems to me to have a great degree of probability.  And I agree with Dr. Wyville Thomson against Sir Charles Lyell (it takes two of us to have any chance against his authority) in demurring to the assertion that “to talk of chalk having been uninterruptedly formed in the Atlantic is as inadmissible in a geographical as in a geological sense.”

If the word “chalk” is to be used as a stratigraphical term and restricted to Globigerina mud deposited during the Cretaceous epoch, of course it is improper to call the precisely similar mud of more recent date, chalk.  If, on the other hand, it is to be used as a mineralogical term, I do not see how the modern and the ancient chalks are to be separated—­and, looking at the matter geographically, I see no reason to doubt that a boring rod driven from the surface of the mud which forms the floor of the mid-Atlantic would pass through one continuous mass of Globigerina mud, first of modern, then of tertiary, and then of mesozoic date; the “chalks” of different depths and ages being distinguished merely by the different forms of other organisms associated with the Globigerinoe.