taken place in the course of development of the crocodilian order. These changes consist in the advance forwards of the external nares, the more posterior location of the internal nares, the increasing irregularity of the alveolar borders and sizes of the teeth, and the change from amphicœlous to procœlous vertebral articulations.

Prof. Owen proposes that these changes were concomitants of a gradual restriction of aquatic and increase of terrestrial habits, and the gradual diminution of a purely fish diet, and the adoption of land animals as food. The capture of the latter and their retention below the surface of the water until devoured, directly relate to the uses of, and hence necessity for, the new structures in question.

A NEW DIADECTES.-This very singular genus1 of supposed Saurians, is represented by a third species from the Permian of Texas. The teeth are more completely molar in their character than in the species already described, being in the unworn condition as broad across the crown, as the latter is high. In the transverse direction the crowns are two and half times as long as wide. The extremities are rounded, and there is a median cusp extending across the crown; on each side of the cusp, the face of the crown is slightly concave. The enamel is strongly but finely wrinkled. The tooth series terminates abruptly in a tooth of half the transverse extent of the penultimate. Length of space occupied by penultimate and ante-penultimate teeth M. .021; length of base of penultimate .010; width of do. .024; elevation of crown, least .006; do. at cusp, .009.

This species is larger than those heretofore described, and the teeth are adapted for crushing harder bodies-having perhaps a use like those of Placodus or Pycnodus. It is called D. molaris.

GEOLOGY OF THE BRITISH ARCTIC EXPEDITION.-Geological investigation in the Polar regions is beset with difficulties of so grave a character that very few collections have hitherto been brought home by Arctic explorers, and these have necessarily been meagre. During Sir George Nares' expedition, however, special attention was paid to geological observations wherever practicable, and Captain Fielden thus contrived to collect more than two thousand specimens of rocks and fossils. He also had the good fortune to find his collections brought home in safetya fact worth mentioning, because some other fine collections have been lost to science through the mishaps incident to Arctic traveling. The recently formed collections, and the results deduced from their study, were lately laid before the Geological Society. In working out the stratigraphical results, Captain Fielden has had the benefit of Mr. de Rance's aid, and in the palæontological department that of Mr. Etheridge. The fundamental rocks 1 American Naturalist, 1868, May, p. 327.

of the area under examination consist of gneiss which is probably of Laurentian age, the Canadian rocks extending into Polar area. These are followed by unfossiliferous slates and grits, known as the Cape Rawson beds, which are evidently older than the fossilbearing Upper Silurians. It is proved, indeed, by the recent expedition, that Lower Silurian rocks exists in Grinnell and Hall Lands, thus disproving Murchson's view that the Polar area was dry land during the Lower Silurian period. Sixty species of fossils have been determined by Mr. Etheridge, ranging from the Lower to the Upper Silurian, and including some characteristic forms of Llandecilo and Wenlock age. The cream-colored dolomites found in abundance by some of the previous explorers are believed to represent the whole of the Silurian, and perhaps part of the Devonian period. True marine Devonians have been discovered for the first time in Grinnell Land. Here, too, the carboniferous limestone was found rising to a height of 2000 feet. This formation extends to the most northern point yet reached, and probably strikes beneath the Polar Sea to Spitzbergen. About thirty species, chiefly Brachiopods and Polyzoa, were procured from the carboniferous limestones of Cape Joseph Henry, the most northerly of the twenty localities from which fossils were collected.

Mr. Etheridge points out the greater resemblance of the Arctic palæozoic fauna to that of America than to that of Europe. No mesozoic rocks are known until we reach the cretaceous strata, which are represented in Greenland by plant-bearing beds that indicate by their fossils a warm climate something like that of Egypt at the present day. The vegetation of the miocene beds in the Arctic regions points to climatal conditions about thirty degrees warmer than those which at present prevail. The miocene beds of Grinnell Land contain the common fir (Pinus abies) the birch, poplar, and other trees similar to those which occur in Spitzbergen. A seam of miocene coal, thirty feet in thickness, was discovered by the expedition at Lady Franklin Sound.-Academy.

GEOGRAPHY AND TRAVELS.1

COLONEL PREJEVALSKY'S THIRD JOURNEY.-This distinguished Russian explorer has sent, under date of August, 1877, to the Russian Geographical Society, a report of a third journey in Central Asia. Translations of this report have been made by Dr. Petermann, published as a supplement to his Mittheilungen, with the original route maps and an Uebersichts-Karte of his journeys from 1872 to 1877; and also by Dr. R. Kiepert for the Globus. At the meeting of the Berlin Geographical Society, on the 6th of April last, Herr Von Richthofen read a very interesting paper upon the results of this journey. Colonel Prejevalsky was most fortunate

1 Edited by ELLIS II. YARNALL, Philadelphia.

in making this exploration at a period when this region was held by Yakub-beg, at that time the ruler of Kashgar, who was assassinated about the middle of last year, and his kingdom overthrown by the Chinese. Neither a year earlier, nor at the present time, would such an expedition have been practicable. Leaving Kuldja, August 12th, 1876, he traveled in a general south-east direction, crossing the eastern Tian-Shan by a pass 9800 feet in height, called the Narat, and found that the rain-fall was plentiful on the north side where are abundant forests and game, but wholly deficient on the south side. He then entered upon an extensive plateau called Yuldus, about 8000 feet above the sea. Both in birds and mammalia the Yuldus is very rich. By a pass 9300 ft. in height he descended from this plateau, and before entering Korla (2600 feet, population 6000), on November 4th, 1876, he left behind the last spurs of the Tian-shan. Proceeding to the Valley of the Tarrim he passed a stony strip of country, probably the shore of a former sea, while beyond is a desert consisting of clay and sand. The clay is impregnated with salt, and on both sides of the Tarrim salt marshes are are found. On December 18th he arrived at Charchalyk, between the Lob-Nor lake and the lofty mountains of Altyn-tag. He explored the northern slope of this range, which rises precipitously, as an immense wall, to the height of 12,000 to 14,000 feet. South of the Altyn-tag, it was learned, is a plateau of 13,000 feet in height, and beyond, other ranges of mountains, forming an enormous mountain chain covered with perpetual snow. The Tarrim and Lob-Nor desert is the poorest and most desolate region Prejevalsky had ever set eyes on. He then explored the northern face of the Altyn-Tag range which forms the northern escarpment of the Tibetan plateau. The mountains are about 14,000 feet high. These mountains, says the account in the Geographical Magazine, are characterized by great sterility, and it is only in the valleys and ravines that vegetation grows; yet, nevertheless, large swarms of locusts are here to be seen. In the summer of 1876 they committed great ravages, and rose to a height of 9000 feet in the mountains. The climate of the Altyn-Tag is characterized on its northern side at least by great cold and little snow. In summer, according to the natives, it rains frequently and is very windy. In this mountain region and the adjacent Kum-Tag desert there are a few wild camels, which twenty years ago were said to have been very common. They seek the upper valleys of the Altyn-Tag in the summer and the most inaccessible deserts in the winter. Their sight, sense of hearing and of smell are exceedingly quick, a striking contrast to the domesticated camel, which is just the opposite. Lob-Nor lake is supplied by the Tarrim river; it is shallow, overgrown with reeds and is for the most part a morass, the water being fresh, though there are salt marshes all around it. The inhabitants about the lake speak a language most like that of Khotan. The

exploration was made just before the invasion of the Chinese, the inhabitants being of Aryan stock and of the religion of Islam.

The Lob-Nor lake is elliptical in shape, is 90 or 100 versts in length and 20 versts in breadth. It is 2200 feet above the sea level. It is much overgrown with weeds, and, though surrounded by salt marshes, the water is clear and sweet.

The flights of birds of passage which make a resting-place of Lob-Nor in their migrations, were very carefully observed by Prejevalsky, millions during February passing on their way across the desert. None came from the south across the lofty and cold plateau of Tibet, but cross it where it is narrowest, i. e., in the direction of Khotan. The region explored by Prejevalsky lies to the north of Tibet. The article is illustrated by a map

On all sides, this great depression, forming a basin surrounded by the loftiest mountains of the globe, has been approached by the English and Russians, but never visited by any scientific or intelligent travelers. On our maps this basin of the Lob-Nor has been placed far beyond the great central mountain range of the Kuen-Lun, and nearer the Tian-shan system; whereas, according to Prejevalsky, it lies at the foot of the Altyn-tag, which he believes is, without doubt, the northern rampart of that mighty region of mountain and plateau, whose southern boundary rises over the plains of India, and thus extends in breadth over nearly thirteen degrees latitude-a distance equal to that from Naples to Hamburg.

In concluding his examination of the results of this very successful exploration, Herr Von Richthofen remarks that new discoveries bring new problems, as, for instance, the existence of a body of fresh water in a spot where all former accounts tell of a great salt sea, and where every theoretical conclusion would confirm us in the belief that such was the case. Count Béla Szécsenyi has already departed from Shanghai with the expectation of reaching the southern side of the Tarrim basin.

Meanwhile Col. Prejevalsky left Kuldja on August 28th, 1877, for Guchen, intending to penetrate into Tibet by Hami, Tsaidam and the upper course of the Yang-tse. Unfortunately, after reaching Guchen, sickness obliged him to return to Zaissan, and he is now on his way home to St. Petersburg.

A more recent journey by Captain Gill, in Western China, supplies, states the Geographical Magazine, an interesting confirmation of the apparent existence of a belt of exceedingly moist region between the Tibetan plateau and the lands encompassing it on its north-eastern and eastern sides. Prejevalsky, in his "Mongolia and Tangut Country," notices this feature while ascending the mountains south-west of Tajing; the Père Armand David noticed it during his residence at Mupin, north of Chingtu-fu; Mr. Cooper, while making his way from the last-named

place into eastern Tibet; and Captain Gill's testimony now supplies us with a link between the observations of Prejevalsky and David, as he speaks of the wonderfully moist and semi-tropical character of the vegetation on the eastern side of the plateau, between the valleys Sung-pan-ting and Ling-ngan, on the extreme northern border of the province of Se-chuen.

DUTCH ARCTIC EXPEDITION.-The Willem Barentz, a twomasted schooner of eighty tons, built expressly for this service, with a crew of fourteen men, three officers, a zoölogist, a doctor, a photographer and eight sailors, sailed from Ijmuiden on the 5th of May, upon what may be regarded as an experimental voyage to Jan Mayen Island, thence to Spitzbergen, examining the edge of the ice en route, and calling at Amsterdam Island. Afterwards they hope to visit Novaya Zemlya and the Barentz Sea, returning home in October. Deep sea soundings will be made, and observations taken of the fauna, and flora; strength, and direction of currents; in magnetism, and meteorology. The expedition is supported by the contributions of Dutchmen.

GEOGRAPHICAL NEWS.-The last (June) number of Petermann's Mittheilungen contains a very interesting account of the application of the process of helio-gravure, by the Austrian Military Geographical Institute, to the production of the new maps of the Austro-Hungarian Empire. The maps are prepared on a scale of 1-60,000, and reduced photographically to a scale of 1-75,000. The (sun) engraving upon copper by the new process requires only about four weeks, whilst the engraving by hand would need forty-two months. The first sheets of this new map were issued in 1873; and, at the end of 1877, 271 were published, and it is expected that the whole number (715) will be completed within 10 or 12 years from the commencement of publication; whereas by the usual method a period of fifty to sixty years must have elapsed before the accomplishment of the work. The cost of the new process is only one-fourth that of the old. As regards the artistic appearance of these maps a specimen given in the Mittheilungen is most favorable; the impression being clear and sharp, and likely to deceive even an engraver.

The first volume of Dr. F. Ratzil, on the Geography of the United States, relating to physical geography, has lately been published. A second volume, on Social Geography, will next

appear.

The Geographical Magazine, for June, gives the results of Nares' Narrative of a Voyage to the Polar Sea during 1875-76. Also a very complete map of the African Lake Region, with a notice of the advance sheets of Stanley's book. The map marks an era in African cartography. The review closes with this paragraph "Great as the value of Mr. Stanley's geographical research