300 



THE GEOLOGIST. 



I quoted then as a few instances the Cyprcea sanguinolenta, Buccinum 

 lyratum, Oliva flammulata ; 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 then 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 his report, un- 

 hesitatingly represents the desert as having been once widely inundated 

 £IS £L SGcL" gulf, which broke in through the Gulf of Gabes, and the unmis- 

 takable traces of which are still to be seen by the 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 mollusk 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 far 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. 



With 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 propagatory circuit as far as Senegal, — such as the Lutraria oblonga, 

 Tellina crassa, T lacunosa, Venus ovata, and three out of four of our 

 DosinisB, namely the Dosinia exoleta, 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 Tug on anatina and Adanson's vagal, the Tellina 

 strigosa. The great Mactra Bucklandi, 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 configura- 

 tion of the district and the constitution of the soil. Earth, on his journey 

 from Tripoli to Murzuk, in following the old Koman 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-Earopean, 

 namely, on the one side with that of the Pj-renean peninsula, and on the 

 other with that of Southern Italy ; whilst in Senegal, Gambia, and 

 the other countries beyond the desert to the Nile, 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^ contains numerous proofs of this, and these are 

 multiplied at every fresh comparison. The crossing of the Inuus ecau- 



* Bull. Soc. Geol. 1857, t. xiv. p. 615. 

 t Petermann, Mitth. 1861, t. xiii. 

 \ 3 vols. Leipsic, 1841. 



