202 
NAPOURE 
[ DECEMBER 27, 1906 
a belt of alkaline rocks surrounds the 
African continent. 
The extensive collections of fossils brought home 
by the members of the Foureau-Lamy mission were 
placed in the hands of the late Prof. Munier-Chalmas 
for description, and on the lamented death of that 
palzeontologist were transferred to his successor, Prof. 
Emile Haug. Valuable assistance in the work of 
determining and describing these fossils was received 
from Profs. Zeiller and Douvillé and from M. and 
Madame Qéhlert. The result of these studies is to 
show that, in addition to the granitic and meta- 
morphic rocks which at present cover such wide 
areas in the French Sahara, fossiliferous strata belong- 
ing to the Silurian, Devonian, Carboniferous, and 
Cretaceous systems also occur. 
At a place called Tindesset, about 764 miles due 
south from Philippeville, there is found a series of 
igneous 
Fic. 3.—The larger specimens illustrate the fine fretted patterns produced 
on the surfaces of limestone rocks by the continued action of impinging 
sand grains driven by the wind. The four smaller specimens (17, 18, 
19 and 20) illustrate the wearing down of fragments of siliceous rock, 
acted on by the natural ‘*sand-blast.'’ These are similar to those 
described by Mr. Enys from New Zealand. 
shales cropping out from below the Devonian sand- 
stones. The point at which they occur is nearly 
4000 feet above the sea, and was reached with great 
difficulty by the members of the expedition. On 
splitting specimens of these shales that were brought 
home, the late Prof. Munier-Chalmas found undoubted 
examples of graptolites belonging to the genus 
Climacograptus. At that time strata of Silurian 
age were not certainly known to exist in the 
Sahara or in any part of northern Africa, but sub- 
sequently M. Flamand described graptolite shales 
as occurring in the Sahara at a locality about 250 
miles north-west of Tindesset. As these belong to 
the Llandovery (Gothlandian) stage, the fossils of 
Tindesset may not improbably be referred to the same 
age. 
NO, 1939, VOL. 75 | 
The Devonian strata cover a wide area in the 
northern part of the district traversed by the mission. 
Strata of this age were recognised by Overweg so 
far back as 1850, the fossils being determined by 
Beyrich. In the district of Tassili they form a plateau 
consisting of sandstones passing into quartzites. 
Besides the obscure fossils referred to, Spirophyton, 
Arthrophycus, Nereites, Crossopodia, Nemertites, and 
Medusina, undoubted examples of Homalonotus, 
Melocrinus, and various brachiopods occur, which 
justify the placing of these strata at the very base 
of the Devonian. In addition to these, a number of 
separate valves of a lamellibranch shell, mineralised 
by haematite, were found. These are referred by 
Munier-Chalmas to a new genus (Desertella), and the 
beds containing them are doubtfully assigned to the 
Middle Devonian. 
The Carboniferous system, also first recognised in 
North Africa by Overweg and Beyrich, has been 
found at’ many points in the Algerian Sahara, and a 
fairly large series of fossils (principally plants and 
brachiopods) was brought back by the members of 
this mission. The strata of sandstone and lime- 
stone appear to rest quite conformably upon the 
Devonian sandstones, and to represent low horizons 
in the Carboniferous system (Ouralian and Mosco- 
vian). As is well known, Upper Carboniferous strata 
also. occur over considerable areas in North 
Africa. 
The Cretaceous strata consist of the widely-spread 
beds of limestones forming extensive plateaux, and 
containing Ostrea columba with other characteristic 
Cenomanian fossils. The escarpments formed by 
these limestone plateaux have a height of from 300 
feet to 350 feet, and at their base it has long been 
known that variegated clays with beds of gypsum 
occur. Up to the time of the dispatch of the 
Foureau-Lamy mission, however, no fossils had been 
found in these beds, and their age remained doubtful. 
The discovery of the remains of Cretaceous types of 
Ceratodus with other fishes and some reptilian bones 
led Munier-Chalmas to assign these strata to the 
same age as our Gault. 
In addition to the fossiliferous rocks referred to 
above, tracts of sandstone strata, which yielded no 
trace of fossils, were found, and the exact geo- 
logical age of these must remain for the present in 
doubt. 
Two plates of the work are devoted to illustrations 
of the structures developed in limestone rocks by 
zolian action—the impinging on rock-surfaces of 
sand grains driven by the wind. These are well 
known to all geologists who have studied desert 
formations, but the examples so beautifully figured 
in this work are of exceptional interest (see 
Big. 3): 
In the ethnographical section of this volume, which 
is very full and admirably illustrated, facts of very 
considerable geological interest are recorded. Most 
important of these is the account of the occurrence 
of implements formed of sandstone and quartzite, 
which are of undoubted Palaeolithic types. The whole 
of the ten examples appear to be of the large, 
elongated, and pointed form so common at Saint- 
Acheul, none of the smaller oval type having been 
found. Neolithic types of both polished and un- 
polished implements abound, and are very fully illus- 
trated. i 
Both the authors and publishers of this very 
important worl are to be heartily congratulated on 
the discoveries made and the manner in which they 
are given to the world. ¥ 
Jo were 
