156 THREE CRUISES OF THE “ BLAKE." 
and more constant, or even in the deeper regions perfectly 
uniform, species of the most varied derivations, when they had 
once attained a certain zone, could spread everywhere. This 
explains at once how the deep-water fauna presents a very uni- 
form composition in all regions of the globe, but at the same 
time includes various species the analogues of which live in the 
sublittoral regions of both cold and hot climates, and may have 
sent an occasional wanderer into deeper waters. 
While the little dredging thus far done in deep water has 
added to our knowledge a large number of antique types which 
strongly remind us of tertiary, cretaceous, and even of jurassic 
forms, we should not forget that such antique types occur 
everywhere, in limited numbers, it is true, both in the shallower 
regions of the sea and in fresh water. We can only say that 
in the deep-water fauna a relatively larger number of such 
antique forms has been found than elsewhere. In contrasting 
the littoral with the continental and the abyssal fauns, the 
last shows a closer affinity to types of a former period than 
does the fauna living at higher levels, where the descendants 
of antique types are also met, but have become familiar from 
their common occurrence. There are in deep waters no ga- 
noids ; to-day their representatives are found in the fresh waters 
of Australia (Ceratodus) and of North America (Lepidosteus). 
Neither are there any deep-sea graptolites or belemnites. 
Old-fashioned animals like Trigonia, Limulus, and Lingula are 
all from shallow water, as are also Amphioxus and Cestracion. 
No species of characteristic palzeozoic corals have been dredged, 
and nothing resembling the remarkable crinoids, so abundant in 
former times. The affinities of the deep-sea types recall to us 
mesozoic and. cainozoic types, such as we find in the chalk and 
tertiaries. No such old-fashioned animals have been discovered 
as throw new light on our zodlogical knowledge, although, as 
Moseley well says, in our deep-sea explorations we obtain for 
the first time a glimpse of the fauna and flora of nearly three 
quarters of the earth’s surface. Our whole knowledge of the 
sea bottom has been created within a few years; before that 
time we knew little of its fauna and flora beyond what is found 
on a comparatively narrow belt of the coast line. 
