TERTIARY MAMMAL HORIZONS. 37 



the younger river alluvia, lake bottoms, aeolian sands, peats and 

 mosses. 



Geographic Changes. — The beginning of the Pleistocene is 

 remarkable for its broad land connections and it represents the 

 last stage of that community of fauna which during the Pliocene 

 distinguished the entire region of P>urope, Asia and Africa. The 

 mid-Pleistocene period in Europe is mainly one of continental 

 depression ; (i) at the climax of the first glacial advance exten- 

 sive portions of northern Europe were submerged beneath the 

 sea ; (2) at the close of the first interglacial or temperate period 

 (Elephas antiquus stage) occurred the volcanic disturbances in 

 Central Europe and the hot spring formations of Thuringia 

 (Taubach, Weimar) ; at this time all the old contiiioital connec- 

 tions characteristic of the Tertiary and serving as land bridges for 

 free Holarctic, Oriental and Ethiopian migration began to break 

 np in the follozving manner : during the early mid- Pleisto- 

 cene or Elephas antiquus stage (Pohlig) the English Channel 

 broke through the long preexisting land-bridge between Eng- 

 land and France ; Great Britain was faunally isolated ; simi- 

 larly the Irish Channel was depressed and Ireland lost its 

 land connection with Wales in the early Pleistocene and with 

 Scotland in the newer Pleistocene.^ In the Mediterranean 

 region, also, at the close of the first interglacial period (Pohlig) 

 the land bridge across Gibraltar, also that between Italy, Sicily 

 and Africa was broken ; Malta ^ was isolated as an Island and 

 the great Elephas antiquus dwindled into the small insular t}'pe 

 E. melitensis. To the eastward the Mediterranean extended into 

 the yEgean plateau, which had previously been terra firma, and 

 the ^gean sea cut off the land connection between Greece and 

 Asia Minor. It is important to note as obser\-ed by Wallace 

 and Lydekker, that the arid and desert land connection still ex- 

 isting between Europe and Africa at the Isthmus of Suez consti- 

 tutes practically a faunal barrier as impassable for most mam- 



^ According to Scharff, Ireland has yielded only ten Pleistocene species, includ- 

 ing the Northern Leptis variabilis and Reindeer and the great Megaceros hibernii€, 

 which is found in the post-glacial peat moors. 



2 Malta shows evidences of two periods of elevation and depression. See PoHLiG, 

 also Leith Adams, " The Nile Valley and Malta," London, 1870. 



