370 ORTMANN — DISTRIBUTION OF DECAPODS [Aprils, 



range running north-south. In Algeria we have, according to Lap- 

 parent, 1 deposits of Cretaceous and Eocene age, but only traces of 

 Oligocene, and thus we can place the upheaval of these parts at the 

 end of the Eocene, and probably at this time the connection with 

 Southwestern Europe began to develop. The mountain range 

 along the northern coast of Algiers, as far as the Strait of Gibraltar, 

 consibts of rocks which (see Suess, 1883, p. 293 ff.) are also found 

 in the so-called Betic Cordilleras {ibid., p. 298) in Southern Spain, 

 and the tectonic unity of these ranges of Algiers and Spain is 

 especially emphasized by Suess, as well as their tectonic connection 

 with the Apennines and the Alps. The origin of all these moun- 

 tain chains was near the end of the first half of the Tertiary, about 

 the Oligocene time. 



But this connection of the northwestern parts of Africa and of 

 Southern Spain with the rest of Africa did not constitute a com- 

 plete union with Europe. We know that the central and northern 

 region of Spain, the Iberian Meseta, is an old land, but that to the 

 south and north of it, on the one side along the valley of the 

 Guadalquivir river in Spain, on the other in the region of the 

 Garonne river in France, connections of the Mediterranean Sea with 

 the Atlantic Ocean existed. According to Suess (1885, p. 381 ; see 

 also Neumayr, 1890, p. 516), in the valley of the Guadalquivir 

 there are Tertiary deposits, reaching from the Atlantic to the Medi- 

 terranean Sea, which belong to the first and second Mediterranean 

 stage — that is to say, to the Miocene — while deposits of the third 

 Mediterranean stage (Pliocene) have not been found. Conse- 

 quently this strait (Betic Strait) became dry at the end of the 

 Miocene, and by this process the northern part of Spain was united 

 with the southern and with Algiers and Africa. 



The disappearance of this strait was the last step which resulted 

 in a definitive connection of Africa with Europe, since the strait in 

 the region of the Garonne river, in Southern France, became prob- 

 ably land a little earlier, namely, at the end of the Oligocene (see 

 Suess, 1885, p. 382 if., and Neumayr, 1890, p. 516). 



But it is to be borne in mind that possibly the conditions were 

 not so simple as has been represented above. According to Lap- 

 parent (/. c, pp. 1 29 1 and 13 13), the Betic Strait (détroit bétic, 

 also called Andalusian connection) was dry during the Oligocene, 



1 Tratte de Geologie, Vol. 2, 1893, P- i 2 9 x - 



