Number of Animals in Geological Times. 355 



to as many local faunae of the present period ; for we may repeat, 

 that the fauna of the Seychelles coDtains only 258 species, and 

 that of Mauritius, Bourbon and Madagascar, 275. Nay, upon 

 3000 miles of coast along the western shores of the American 

 continent within the tropics, only twice the number of living 

 species have been obtained as occur respectively in each succes- 

 sive greater subdivision of the palaeozoic system within the nar- 

 row limits of the State of New Yoik only. (See above the results 

 of Professor Adams's investigations upon the coast of Panama.) 



It is a most unexpected and very significant coincidence, that 

 the late admirable iuvestigations of Elie de Beaumont upon the 

 mountain systems have led him to the recognition of nearly ten 

 times as mauy periods of great disturbance in the physical con- 

 stitution of the earth's surface as he himself knew twenty-five 

 years ago, each attended by the upheaval of as many mountain 

 chains, differing in their main direction. The investigations of 

 palaeontologists having an entirely different character, and founded 

 upon facts which until recently have apparently had only a re- 

 mote connexion with the other series of phenomena, have never- 

 theless brought them at about the same time to like conclusions 

 respecting animal life, showing that the periods of disappearance 

 and renovation of organized beings upon the earth have been 

 much more frequent than could be supposed even ten years ago, 

 each set having probably been chat acteristic of one of those long 

 periods of comparative rest inte]vening between two great suc- 

 cessive geological catactysms. 



What is true of Mollusca may be said of all other classes. 

 Among Radiata, are not the coral reefs of the palaeozoic ages as 

 rich in species as any coral reef of the Pacific ? Let us even 

 compare the most extensive lists of corals yet given as belonging 

 to any circumscribed locality, — those of the Red Sea as desnibed 

 by Ehrenberg, those of the Peejee Islands as described by Prof. 

 J. D. Dana, — and let us inquire whether the palaeozoic 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, have 

 not the coral reefs of the oolitic period in Normandy, or in the 

 Jura of Switzerland, and the Alp of Wurtemberg, increased our 

 lists of fossils as largely, and introduced into our zoological works 

 as various forms as are knowu 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 ten 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 geolo- 

 gical formations ? The number of Crinoids found in the single 



23* 



