556 
NATURE 
[ Oct. 8, 1885 
from the Lower Greensand by means of deep borings at any 
great distance from its outcrop. Even if Lower Greensand 
occur at all in such places, it will probably be in reduced thick- 
ness, and therefore with reduced water-capacity. 
American Evidences of Eocene Mammals of the “* Plastic Clay” 
Period, by Sir Richard Owen, K.C.B., F.R.S., G.S., &c.—In 
the year 1843 a fragment of a lower jaw with one entire molar 
of a mammal was dredged up off the Essex coast. A canine 
tooth of the same was found in a well-sinking near Camberwell, 
in piercing the ‘‘ plastic clay.” The author had described the 
above as belonging to an animal of the Lophiodont family, and 
proposed for it the generic name Coryphodon. Shortly after- 
wards De Blainville had noticed certain fossils as ‘‘ probably 
Coryphodont,” but had referred them to Lophiodon anthra- 
cotherium. Ten years later Prof. Hébert had recognised two 
species of Coryphodon in the plastic clay of France. Explora- 
tions by Leidy, Marsh, and Hayden, in the ‘‘ Mauvaises Terres ” 
of Nebraska had led to the discovery of a large hoofed mammal 
allied to Coryphodon, to which the name Zifanotherium had been 
given, and Prof. Cope has now recognised, from Evanstown, 
Wyoming, seven species of Coryphodon. From these materials, 
which have been rendered accessible to European palzon- 
tologists by the superb volume of reports recently issued by the 
United States Government, the author is enabled to give a 
general description of this family of hoofed mammals of large 
size which flourished in early Eocene times. To the details of 
this the major part of the paper is devoted. 
Some Results of the Crystallographic Study of Danburit:, by 
Dr. Max Schuster.—In studying the characters of the faces and 
the structure of the Danburite crystals found in Switzerland the 
author has met with vicinal faces of a peculiar kind, for which 
he proposes the term ‘‘ transitional faces” (7ichermak Min. 
Mittheil., vi., 1884, p. 511). Attention is called to the fact 
that these faces are easily affected by those causes which produce 
an unequal development of fices otherwise symmetrically dis- 
posed, and an illustration is given of the way in which their 
indices are numerically related to those of the principal faces of 
the crystal. 
Notice of an Outline Geological Map of Lower Egypt, Arabia 
Petrea, and Palestine, by Edward Hull, LL.D., F.R.S., F.G.S. 
—The map exhibited was enlarged from that which accompanies 
the author’s book, ‘‘ Mount Seir, Sinai, and Western Palestine,” 
giving a narrative of the expedition sent out into these countries 
by the Palestine Exploration Society in 1883-84. It embraces 
a region extending from the valley of the Nile on the west to 
the table-land of Edom (Mount Seir) and Moab, including the 
Jordan, Arabah Valley, and the mountains of Sinai. Its northern 
limit is the Lebanon. The main lines of fault and dip of the 
strata are also indicated. A topographical and geological map 
of the Arabah Valley on a scale of about six miles to one inch 
was in preparation, and would accompany the Geological Report 
now in the press for the Palestine Exploration Society. 
A Preliminary Note on a New Fossil Reptile recently dis- 
covered at New Spynie, near Elgin, by Dr. R. H. Traquair, 
F.R.S.—Of this most important fossil the author had as yet 
only seen a photograph submitted to him by Prof Judd, the Pre- 
sident of the Section. This photograph represents pretty nearly 
a vertical longitudinal section of a reptilian skull, of which one 
very prominent feature is the presence of a large conical tusk in 
the upper jaw, projecting downwards and forwards, immediately 
behind the premaxillary part of the skull. This tusk is seen 
only in impression, but the cast of the internal cavity which is 
well shown indicates that it grew from a permanent pulp. No 
evidence of any other teeth is visible, and the whole appearance | 
of the skull as seen in the photograph, with the position and 
shape of the tusk, indicate that the reptile here represented, if not 
actually belonging to the genus Dicynodon, is certainly a 
member of the group of Dicynodontia. Geologists will not 
underrate the importance of this discovery in its bearing on the 
question of the age of the reptiliferous sandstone of Elgin. 
On the Average Density of Meteorites compared with that of 
the Earth, by the Rey. E. Hill, M.A., F.G.S.—The average 
density of the meteorites which fall on the earth is attempted to 
be calculated. Different methods give as results 4°55, 4°58, 
4°84, 5°71, the last value being influenced by the size of one 
particularly large metallic specimen. The average density of the 
earth is usually regarded as 5°6. Meteorites are samples of the 
materials of space. A mass of them would aggregate into a 
body of density not widely differing from that of the earth. 
The densities of the other planets are not inconsistent with a 
like origin, Consequently any theory of the genesis of the earth 
from pre-existing materials involves a probability that an im- 
portant part of its nucleus is metallic. 
On the Occurrence of Lower Old Red Conglomerate in the 
Promontory of the Fanad, North Donegal, by Prof. Edward 
Hull, LL.D., F.R.S., Director of the Geological Survey of 
Ireland.—The district in which the Old Red Conglomerate 
occurs is formed of ridges and valleys of metamorphic rocks, 
consisting of beds of quartzite, schist, crystalline limestone, and 
trap, chiefly diorite. It lies between Lough Swilly and Mulroy 
Bay, and is washed on the north by the waters of the Atlantic. 
The remarkable tract of the Old Red Conglomerate, recently 
discovered by the officers of the Geological Survey, is far remote 
from any mass of the same formation, and it is unrepresented 
on any geological map hitherto published. The beds consist of 
red and purple sandstones and conglomerates, made up chiefly 
of quartzite pebbles and blocks, but also containing others of 
limestone and trap ; all derived from the surrounding metamor- 
phic series. They occupy an area of over two miles in length 
and half a mile across, extending along the northern base of 
Knock Alla, a ridge of quartzite which traverses the promontory 
from side to side. The beds dip against the base of the moun- 
tain, against which they are let down by a large fault, and they 
terminate along their northern edge by an unconformable super- 
position on beds of quartzite and limestone. They reach a total 
thickness of about Soo feet. From the position of these beds it 
becomes evident that they are unconnected with any of the 
recognised basins of Lower Old Red Sandstone, either in Scot- 
land or Ireland, and may, therefore, be regarded as having 
been formed in an isolated basin, which, following the example 
of Dr. Geikie, I may be allowed to name ‘‘ Lake Fanad.” 
The tract will be a new feature on geological maps of 
Treland. 
On Bastite-Serpentine aud Troktolite in Aberdeenshire ; with 
a Note on the Rock of the Black Dg, by Prof. T. G. Bonney, 
D Se., LL.D., F.R.S., Pres.G.S.—Bastite-serpentine (as noticed 
some time since by Prof. Heddle) occurs near Belhelvie and on 
the shore near the Black Dog. The author describes the micro- 
scopic structure of this, showing that it consists of olivine and 
its alteration products, enstatite in various stages of alteration, 
and a mineral of the spinellid group. Associated with this in 
the Belhelvie district is a fairly normal troktolite, consisting of 
a_plagioclastic felspar allied to anorthite, olivine, more or less 
altered, and a little diallage. It closely resembles the typical 
Volpersdorf rock, but has rather less magnesia and more 
alumina, corresponding chemically more nearly with a rock de- 
scri>ed by the author from Coverack Cove, Cornwall. He is of 
opinion that the two rocks differ somewhat in age, though 
probably the earlier was still at a high temperature when the 
latter was intruded, and he inclines to the view that the ser- 
pentine is the older rock of the two. The Black Dog has been 
incorrectly described as consisting of ‘‘ crystals of ¢a/e matted in 
such confusion as to form both a tough and hard rock.” The 
rock really consists of quartz, sillimanite, two kinds of mica, 
an iron oxide (hematite ?), and most probably some dichroite, 
with perhaps a little kyanite. In short, the rock presents a very 
close resemblance under the microscope to some specimens of 
the well-known ‘‘ cordierite gneiss” of Bodenmais. 
On the Re-discovery of Lost Numidian Marbles in Algeria and 
Tunis, by Lieut.-Col. Playfair, H.M. Consul-General for 
Algeria and Tunis. —The author explained that the name itself 
was a misnomer, as they are not found within the limits of 
Numidia proper, but in the province of Africa and in Mauritania. 
Most of the ‘‘ Giallo antico” used in Rome was obtained from 
Simittu Colonia, the modern Chemton, in the valley of the 
Medgérda, the quarries of which are now being extensively 
worked by a Belgian company; but the most remarkable and 
valuable marbles are found near Kleber, in the province of 
Oran, in Algeria. There, on the top of the Montagne Grise, 
exists an elevated plateau, 1500 acres in extent, forming an un- 
interrupted mass of the most splendid marbles and breccias 
which the world contains. Their variety is as extraordinary as 
their beauty. There is creamy white, like ivory ; rose colour, 
like coral ; Giallo antico ; some are as variegated as a peacock’s 
plumage ; and on the west side of the mountain, where there has 
been a great earth-movement, the rock has been broken up and 
re-cemented together, forming a variety of breccias of the most 
extraordinary richness and beauty. 
On some Roch-Specimens from the Islands of the Fernando 
Noronia Group, by Prof. A. Renard, LL.D.—The rock-speci- 
