DEEP-SEA FORMATIONS. 143 
of the oceanic fauna and flora of the present day are found 
within the hundred-fathom line. In attempting either to define 
or to contrast the fauna of the shores and of the deep, we find 
a neutral region, characterized perhaps by no forms strictly its 
own, but in which the stragglers from each zone flourish, and 
nothing typical either of the littoral or of the deep-sea fauna 
is any longer found. 
In many localities where deep-sea deposits are taking place at 
the present day, the distance from the coast is often not very 
great, especially in volcanic regions. Along the face of the 
whole Atlantic coast from the. Bahamas to St. Thomas, the line 
between the continental curve and the two-thousand-fathom line 
is nowhere more than fifteen miles distant. We cannot there- 
fore infer that because a formation has been deposited. parallel 
to a continental coast it must necessarily be a shallow-water 
formation. What to-day would be called continental forma- 
tions, from the character of their fauna, lie within the limits of 
say three hundred and fifty to seven hundred and fifty, or per- 
haps one thousand fathoms. But as the character of the fauna 
in its turn depends mainly upon the constitution of the bottom, 
this interdependence introduces many variable elements. There 
is no greater contrast than that which exists between the fauna 
living upon the recent limestones of the steep slopes of the 
Florida plateau and that found at similar depths in the calca- 
reous ooze of the trough of the Gulf Stream in localities not 
many miles distant. 
We are justified in considering deposits containing large 
amounts of globigerina, radiolarian, and diatom mud as pelagic 
deposits laid down at certain distances from land in considerable 
depths ; but, as these animals are pelagic, the possibility exists 
of their being found in. shallow deposits. Pelagic foraminifera 
are found in the muds which have been brought down by rivers 
into the Gulf of Mexico. The modern greensand found off 
the coast of the Carolinas on the edge of the Gulf Stream 
occurs in depths of less than fifty fathoms. Arenaceous fora- 
minifera are to-day only found in large quantities in deep 
water. 
If, as Wallich suggests, flints are now formed only in deep-sea 
