300 
THE GEOLOGIST. 
I quoted then as a few instances the Cyprcea sanguhiolenta, Buccinum 
lyratum, Oliva Jiammulata ; and I inferred, according to my notions of 
the Great Sahara, that there was at one time a sea extending from the 
Gulf of Gabes southwards as far as the heights of Idijl, in the province of 
Aderer ; thus uniting the Senegambian shores with those of the Me- 
diterranean. I was able even tlien to refer also to the detailed statements 
of M. Laurent,* who had been commissioned with the construction of arte- 
sian wells on the northern border of the desert, and who, in liis report, un- 
hesitatingly represents the desert as having been once widely inundated 
as a sea-gulf, which broke in through the Gulf of Gabes, and the unmis- 
tiikable traces of which are still to be seen by tlie numerous terraces along 
the southern border of the Aoures Mountain, where the ancient seashores 
can even now be recognized by the presence of one of the most common 
inhabitants of the Mediterranean, the Cardium edule, the shells of which 
are there scattered abundantly, and which moUusk seems even yet to be 
found still living in some solitary pools in the desert. I added further, that 
even at present large extents of the desert are situated fjir below the level 
of the sea, and that from the oldest times the extensive salt-crusts and 
salt-marshes have been considered evidences of a former overflowing of the 
sea. 
Witli the progress of M. Homes' labours, the impression of the cor- 
rectness of these statements has increased. We have been not only made 
acquainted with many species amongst the bivalves, which now extend 
their propagator}'^ circuit as far as Senegal, — such as the Lutraria ohloncja, 
Telliua crassa, T. lacunosa, Venus ovata, and three out of four of our 
Dosiuiae, namely the Dosinia exoletci, D. lineta, and D. Adansoni, — but we 
find also in our basin special and very marked Adansonian types, which 
at the present time are only to be found living on the Senegambian coast, 
as, for example, the Tugon anatina and Adanson's vagal, the Tellina 
strigosa. The great Mactra Buclclandi, also, which does not live on the 
European coast at all, seems to appear on the Senegal. 
All accounts of the desert agree in the supposition of a former overflow ; 
and not only Laurent, but also many other naturalists, independently of 
palseontological data, were led to this conclusion solely by the contigura- 
tion of the district and the constitution of the soil. Earth, on his journey 
from Tripoli to Murzuk, in following the old lloman road, seems to have 
moved almost always eastwards of and outside the range of the ancient 
sea ; it might not, therefore, at a future time, be without interest to inves- 
tigate how far the outlines of this old sea correspond with the statements 
of Duveyrier on the limits of the country. f 
The present land-fauna of Morocco and Algiers, as far as Cyrenaica, 
corresponds entirely in its essential features with the South-European, 
namely, on the one side with that of the Pyrenean peninsula, and on the 
other with that of Southern Italy ; whilst in Senegal, Gambia, and 
the other countries beyond the desert to the xVile, the first really African 
types appear. The elephant, rhinoceros, hippopotamus, giraffe, cro- 
codile, and many other principal forms, do not overstep the Sahara ; and the 
contrast between the Morocco-African land-fauna, and the proper African 
fauna is, in most classes of animals, very striking, whilst the connecting 
links with Europe are unmistakable. The voyage of M. Mor. Wagner 
in the regency of Algiers ;J: contains numerous proofs of this, and these are 
multiplied at every fresh comparison. The crossing of the Inuus ecau- 
* Bull. Sdc. Gcol. 1857, t. xiv. p. 615. 
t Pcterinaun, Mitth. 1861, t. xiii. 
^ 3 vols. Leipsic, 1841. 
