A New TÆniopteroid Fern and its Allies. By David White. (Bulletin Geological Society of America, 4 pp., 119–122, pl. I.).

Mr. White has described, under the name of TÆniopteris missouriensis, a new and well characterized fern from the Lower Coal-measures in the vicinity of Clinton, Henry County, Missouri. Botanically, it is of particular interest in that it combines the so-called tÆniopteroid and alethopteroid types of structure, while geologically it is of much value in supplying a readily identified stratigraphic mark in a part of the Carboniferous not especially rich in fossil plants. After thoroughly describing it and considering its specific and generic resemblances, the author discusses at length its suggested genetic relations and represents in a graphic manner a scheme of its probable ancestors and line of descent.

F.H.K.

Rainfall Types of the United States. Annual Report by Vice-President General A.W. Greely. (The National Geographic Magazine. Vol. V., April 29, 1893, pp. 45–58 pl. 20).

The paper confines itself to the characteristic distribution of precipitation throughout the year and gives the rainfall types of the country.

(a) The best defined type of rainfall within the United States is that which dominates the Pacific coast region as far east as western Utah. The characteristic features are a very heavy precipitation during midwinter, and an almost total absence of rain during the late summer. (b) The characteristics of the Mexican type, dominating Mexico, New Mexico and western Texas, are a very heavy precipitation after the summer solstice and a very dry period after the vernal equinox. August is the month of greatest rainfall, while February, March and April are almost free from precipitation. (c) The Missouri type covers the greatest area, dominating the watersheds of the Arkansas, Missouri and upper Mississippi rivers, and of lakes Ontario and Michigan. It is marked by a very light winter precipitation, followed in late spring and early summer by the major portion of the yearly rain, the period when it is most beneficial to the growing grain. (d) The Tennessee type, prevailing in Kentucky, Tennessee, Arkansas, Mississippi and Alabama, has the highest rainfall the last of winter, while the minimum is in mid-autumn. (e) The Atlantic type, covering all the coast save New England, is one where the distribution throughout the year is nearly uniform, with a maximum precipitation after the summer solstice, and a minimum during mid-autumn. (f) The St. Lawrence type is characterized by scarcity during the spring months, heavy rainfall during the late summer and late autumn months, with a maximum during November.

The regions lying between these several type-regions have composite rainfall types, resulting from the influence of two or more simple types.

H.B.K.

The Geographic Development of the Eastern Part of the Mississippi Drainage System. By Lewis G. Westgate, Middletown, Conn. (American Geologist, Vol. XI, April, 1893, 15 pp.)

The drainage of the Eastern Mississippi basin in post-carboniferous was in all probability consequent upon the tilting which accompanied the stronger folds of the Appalachian revolution in the east. The present drainage is found to accord in the main with this hypothetical post-carboniferous drainage, but several streams depart quite widely from it.

(a) The great drainage lines of the St. Lawrence basin are structural valleys developed along the strike of the softer Paleozoic strata, and at right angles to the original surface. The streams seem, therefore, to have adjusted themselves to the differences in hardness and structure of the beds discovered. (b) The Ohio and Cumberland rivers cut directly across the Tennessee and Cincinnati anticlines. The most probable explanation is that the rivers were superimposed upon the arched and eroded Silurian rocks from a thin cover of carboniferous beds—now entirely removed. (c) The Upper Mississippi does not follow the dip of the rocks to the southwest, but follows the strike to the southeast. This part of the river probably dates from the elevation of the plains on the west and the Appalachians on the east, which marked the close of the Cretaceous and which left a broad north and south valley. (d) The author finds good reason to believe that the Lower Mississippi, in post-carboniferous times, flowed west through Missouri and Arkansas. The present course was probably taken at the close of the Cretaceous in consequence of elevations on the west and east, and possible depression in the south.

The Cretaceous base-level recognized by Davis on the Atlantic slope can be traced more or less discontinuously, and remnants of it are believed to exist in Kentucky, Tennessee, Wisconsin, Minnesota and Arkansas. But in general the work of the Tertiary cycle has obliterated almost all evidence of it on all but the hard sandstones and conglomerates of the Paleozoic series. 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.

H.B.K.

On a New Order of Gigantic Fossils. By Erwin H. Barbour. (University Studies. Published by the University of Nebraska. Vol. I, No. 4, July, 1892, pp. 23, pl. 5).

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.

H.B.K.

The Vertical Relief of the Globe. By Hugh Robert Mill, D.Sc., F.R.S.E. Scottish Geographical Magazine, April, 1890.

The purpose of Dr. Mill’s paper is to show a simple yet adequate basis on which to build the superstructure of physical geography. It does not attempt a discussion of the distribution and varieties of vertical relief. The structure of the earth is stated most simply by describing it as an irregular stony ball, covered with an ocean and an envelope of air. If the lithosphere were perfectly smooth and at rest, with the hydrosphere uniformly spread over its surface, the former would have the form of the terrestrial spheroid, and the latter would surround it to a depth of 1.7 miles. The surface of this hypothetical spheroid Dr. Mill calls mean sphere level. Of course, in reality the surface of the lithosphere is not perfectly smooth. Parts of it are greatly depressed and parts much elevated, the latter forming the land of the earth. The writer proceeds to calculate the position of mean sphere level, and in the absence of accurate data he uses the careful estimates of Dr. John Murray, which are as follows: Average depths of oceans = 2.36 miles; average height of land = .426 miles; average thickness of hydrosphere surrounding smoothed lithosphere = 1.7 mile; area of land = 55,000,000 square miles; area of oceans = 141,700,000 square miles. Suppose a block of 55,000,000 of square miles area and 1.7 miles deep to be cut out of the smoothed lithosphere and set down on the surface alongside the depression. No change will take place in the surface of the hydrosphere. If the surface of the 141,700,000 square miles of lithosphere were reduced to uniformity, the whole depressed area would lie .66 mile beneath mean sphere level, and the depth of the ocean becomes 2.36 miles. To raise the land to its actual mean level above the hydrosphere surface, a sufficient quantity of matter must be removed from the depressed area and placed on the elevated block. Let x = the thickness of the belt removed and y equal the thickness of the belt when placed on the elevated block. Then x + y is the height of the land above the actual hydrosphere level. From the data given the following equations are easily obtained:

The average height of the land above mean sphere level is thus 1.7 + .306 = 2.006 miles, and the average depth of the depressed portion beneath mean sphere level is .66 + .12 = .78 mile.

Dr. Mill divides the earth into the three following divisions: (1) Abysmal area, occupying all the depressions beneath the mean surface of the lithosphere, occupying 50 per cent. of the earth’s surface; (2) Transitional area, comprising all the regions above mean sphere level covered by the hydrosphere, occupying 22 per cent. of the surface; (3) Continental area, all the lithosphere that projects above the hydrosphere, or 28 per cent. of the earth’s surface.

J.A.B.