and Number of Animals in Geological Times. 279 
Among Radiata, are not the coral reefs of the paleozoic ages 
as rich in species as any coral reef of the Pacific! Let us 
even compare the most extensive list of corals yet given as 
belonging to any circumscribed locality,—those of the Red 
Sea as described by Ehrenberg,—those of the Feejee Islandsas 
described by Professor J. D. Dana,—and let us inquire whether 
the paleozoic rocks of the state of New York do not show as 
great a variety and as large a number of species in their 
_ successive reefs. Again, the coral reefs of the oolitic period 
in Normandy, or in the Jura of Switzerland, and the Alp of 
Wurtemberg, have they not increased our lists of fossils as 
largely, and introduced into our zoological works as various 
forms as are known from any of the most diversified coral 
regions in the world at the present day ? 
Passing from the Corals to the Echinoderms, the question 
may be reversed, and it may be fairly asked whether there 
is any sea shore extending over tens and tens of degrees of 
longitude and latitude, even under the tropics, which has 
yielded as large a number of those Radiata, as occur in 
almost any of the geological formations? The number 
of Crinoids found in the single set of beds known under 
the name of Niagara limestone, equals the whole number 
of Echinoderms found around all the coast of the United 
States. The Crinoids, Echini, and Star-fishes of the oolitic 
period, or any of the subdivisions of that formation, sur- 
pass the number of species of that class which may be 
gathered around the coast of entire continents in the present 
day. The diversity of forms of these animals, comparing 
them with those of the cretaceous periods, is equally great, 
though the Crinoids begin to diminish in number. But the 
variety of Spatangoids and Clypeastroids which come into 
play, compensate largely for the diminution of the family of 
Crinoids. : 
The type of Articulata may seem, in the present condition 
of our knowledge, to form an unanswerable objection to the 
broad statement I have made above, for the hundred thou- 
sands of insects which are known in the present creation will 
hardly allow a comparison with the fossils. But let us ex- 
amine, upon the principles by which we have been guided in 
