CHAP. III.] CONDITIONS AFFECTING DISTRIBUTION. 39 



not only in depressions below the level of the sea but up to a 

 height of 900 feet above it. Borings for water made by the 

 Prench government have shown, that these shells occur twenty 

 feet deep in the sand ; and the occurrence of abundance of salt, 

 sometimes even forming considerable hills, is an additional proof 

 of the disappearance of a large body of salt water. The common 

 cockle is one of the most abundant of the shells found ; and the 

 Eev. H. B. Tristram discovered a new fish, in a salt lake nearly 

 300 miles inland, but which has since been found to inhabit th& 

 Gulf of Guinea. Connected with this proof of recent elevation 

 in the Sahara, we have most interesting indications of subsidence 

 in the area of the Mediterranean, which were perhaps contem- 

 poraneous. Sicily and Malta are connected with Africa by a 

 submerged bank from 300 to 1,200 feet below the surface ; while 

 the depth of the Mediterranean, both to the east and west, is 

 enormous, in some parts more than 13,000 feet ; and another 

 submerged bank with a depth of 1,000 feet occurs at the straits 

 of Gibraltar. In caves in Sicily, remains of the living African 

 elephant have been found by Baron Anca ; and in. other caves Dr. 

 Falconer discovered remains of the Elephas antiquus and of two 

 species of Hi^rjiopotamus. In Malta, three species of elephant 

 have been discovered by Captain Spratt ; a large one closely allied 

 to E. antiquus and two smaller ones not exceeding five feet high 

 when adult. These facts clearly indicate, that when North 

 Africa was separated by a broad arm of the sea from the rest of 

 the continent, it was probably connected with Europe ; and this 

 explains wliy zoologists find themselves obliged to place it along 

 with Europe in the same zoological region. 



Besides this change in the level of the Sahara and the j\Iedi- 

 terranean basin, Europe has undergone many fluctuations in its 

 physical geography in very recent times. In Wales, abundance 

 of sea-shells of living species have been found at an elevation 

 of 1,300 feet; and in Sardinia there is proof of an elevation 

 of 300 feet since the human epoch ; and these are only samples 

 of many such changes of level. But these changes, though very 

 important locally and as connected with geological problems, 

 need not be further noticed here ; as they were not of a 



