chap, m.] 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 
.French 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 saltwater. The common 
cockle is one of the most abundant of the shells found ; and the 
Rev. H. B. Tristram discovered a new fish, in a salt lake nearly 
300 miles inland, but which has since been found to inhabit the 
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 Hippopotamus. 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 why 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 Medi- 
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 
