NATURAL HISTORY OF THE PRIMEVAL WORLD. 



33 



■While the Eocene sub-period was thus prolific of 

 pncliyilerniatons forms, it nourished in its seas, and 

 eiluaries, and rivers, a vast number of new types of 

 hie. Then first appeared tlie corres[)onding species of 

 our existing Lymnea;, Paludiiiw, Planorbes, and other 

 fresh-water shells. The terrestrial snails, Helix, Pupa, 

 Clausilia, and the hke, so rare in earlier epochs, now 

 became abundant. The gasteropods and cephalopods 

 increased in nnmber and variety, and the ocean waters 

 swarmed with busy legions of foraminiferous organisms, 

 whose destiny it was to build up immense masses of 

 nummulitic limestone, rivalling in extent and thickness 

 the coral reefs of the present day. 



Of the shells of the cephalopodous molluscs belong- 

 ing to the tertiary formations, D'Orbigny distinguished 

 between six hundred and seven hundred species. The 

 only genus which our limits will allow us to notice is 

 the NummuUte, so named from the resemblance of the 

 animal to a piece of money. In 

 size it varied from that of a 

 crown piece to microscopic 

 minuteness. It occupies an 

 important place in the history 

 of fossil shells on account of the 

 piodigious numbers in which it 

 is found accum [dated in the ter- 

 tiary strata — often piled upon 

 one another in as close contact 

 Qs the grains in a heap of coin 

 In this state the Nummulites 

 form a considerable portion of 

 the entire bulk of many lofl\ 

 mountains; as in the tertian 

 limestones of Verona and Monte 

 Bolen, and in secondary strali 

 of the Cretaceous period in the 

 Pyrenees, Alps, and Carpath- 

 ians. Some of the Pyramids 

 adds Dr. Bnckland, and the 

 celebrated Sphinx, are com 

 posed of limestone loaded with 

 these Nummulites.* 



It is impossible, says the same distinguished geolo- 

 gist, to see such mountain masses of the remains of a 

 single family of shells thus added to the solid materials 

 of the globe, without recollecting that each individual 

 shell once held an important place in the body of a 

 living animal. And thus may we carry back our 

 imagination to those remote and dim mysterious ages 

 when the ocean waters, which then overflowed the 

 European continent, teemed with swarms of these extinct 

 molluscs, thick as the countless myriads of Berbe and 

 Clio Borealis now living their little life in the polar seas. 



Like the Nautilus and Ammonite, the Nummulites 

 were enabled to float by means of the air-chambers 

 into which the shell was divided. The chambers 

 were numerous, and minutely divided by transverse 

 jiarlitions; they had no siphuncle. In form the shells 

 were orbicular, convolute, without any trace of spire ex- 

 lernall}', and composed of contiguous whorls. Scarcely 

 any of them exceed an inch in diameter. 



We now pass on to the second, or Miocene system of 

 • Of tlie species Ntivimulina dlscoidulis. 



Tertiary deposits, containing an admixture of the extinct 

 genera of lacustrine mammals, with the earliest forms of 

 existing genera. Thus, in the marine formations of 

 Touraine, the fossil remains of Lophiodon, Anoplo- 

 therium, and Pala;otherium have been discovered 

 mingled with bones of the tapir, mastodon, horse, 

 hippopotamus, and rhinoceros.* We shall see, how- 

 ever, that new genera now first made their appearance 

 on the earth, and that the Eocene mammals rapidly 

 became extinct. " One or two of the generic forms," 

 says Professor Owen, " most frequent in the older ter- 

 tiary strata still lingered on the earth, but the rest of 

 the Eocene Mammalia were superseded by new forms, 

 some of them presenting characters intermediate be- 

 tween those of Eocene and those of Pliocene strata. 



Among the Miocene ty pes of life we give the fore- 

 most place to the Dinotlterium, as the largest of 

 terrestrial mammalia. It holds an intermediate place 



Dinotberiiim. 



between the tapir and the mastodon, and thus supplies 

 another valuable extinct link in the great pachyder- 

 matous family. 



The largest species of this genus, Dinotherinm 

 girjanieiim, is calculated by Cuvier to have attained 

 the extraordinary length of eighteen feet. A skull 

 disinterred at Epplesheim, in Hesse Darmstadt, in 

 1836, measured four feet long by three feet broad. 



