of the Canary Zslands. 11 
is exclusively found in the Pacific. Among the 4gathistega 
we find the genus Crucéloculina in the east ; while Biloculina 
Triloculina, and Quinqueloculine are inhabitants of the east 
as well as the west. 
Combining these data, we find, that of the twenty-four ge- 
nera of South America, there are ten common to the two 
sides, two are peculiar to the Pacific, and twelve to the At- 
lantic ; or, what is the same thing, twenty-two genera live on 
the shores of the Atlantic, and only twelve on those of the 
Pacific. If we ask the cause of this great difference in the 
number of species, and especially of the genera, between the 
two coasts of South America, we shall perhaps find a satis- 
factory explanation in the peculiar configuration of the two 
shores. Owing to the proximity of the Andes, the coasts of 
the Pacific are so steep, and the descent so abrupt, that no 
soundings can be obtained at a very short distance from land, 
viz. at little more than half an English mile ; thus a narrow 
stripe only remains for the Foraminifera, and sometimes they 
cannot live at all. On the shores of the Atlantic, on the other 
hand, the gentle slope of the land from the Andes to the sea 
is continued in the bottom of the sea, so that at a distance of 
more than two degrees from the coasts “there is still a depth 
of water suited to the Foraminifera. There is, therefore, on 
this side of America, a broad zone on which the Foraminifera 
are propagated, whose surface is at least ten times as large as 
the other. This double fact affords an explanation of a very 
important question—that as to the undoubted influence of 
the configuration of the surface on the composition of the 
series of beings which inhabit it, and also one of the most in- 
teresting applications to geology in the elucidation it offers as 
to the differences of species of fossil coverings of animals in 
contemporaneous formations. 
The rich materials of Cuba, Haiti, St Thomas, Jamaica, 
Martinique, and Guadaloupe, afforded the result that Cuba, 
owing to its wide extent, and to its favourable position as to 
winds and to the currents from all other islands, possesses on 
its coasts all the species of Foraminifera which are met with 
on the shores of the Antilles ; while the Cuba species are not 
distributed in proportion in the other parts of the Archipelago, 
