Page:The Journal of geology (IA journalofgeology11893univ).pdf/437

Good examples of the lowlands excavated from the Cretaceous base-level during the Tertiary cycle, are the Valley of the East Tennessee and the central lowland of Kentucky and Tennessee. During the post-Tertiary sub-cycle the larger streams trenched to greater or less extent these lowlands. No attempt is made to carry the history of the development of the Mississippi drainage into the complicated chapter of the ice-invasion.

A part of Sioux County, Nebraska, lying north of the Niobrara River, has yielded a new order of gigantic Miocene fossils unlike anything heretofore known. They are best described as fossil corkscrews, of great size, coiling in right-handed or left-handed curves about an actual axis or around an imaginary axis. The screws are often attached at the bottom to an immense transverse piece, rhizome, underground stem, or whatever it may be, which is sometimes three feet in diameter. In other cases the corkscrew ends abruptly downward, as it always does upwards. In still other cases the transverse piece is variously modified, and sometimes blends into the sandstone matrix, as if the underground stem, while growing at one end, was decaying at the other. The fossil corkscrew is invariably vertical, and the so-called rhizome invariably curves rapidly upwards, and extends outwards an indefinite distance.

That they could ever have been formed by burrowing animals, by geysers or springs, or by any mechanical means whatever, is entirely untenable. Their organic origin is unquestionable. Microscopic sections show smooth spindle-shaped rods, which are suggestive of sponge spicules. From the numbers seen in place it is evident that they flourished in thickly crowded forests of vast extent.

A finely preserved rodent's skeleton was found in one great stem. The probable explanation is not that the rodent burrowed there, but that its submerged skeleton became an anchorage for a living, growing Daimonelix, which eventually enveloped it.

The author proposes this provisional classification:

The different species are described in full.