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Show EltA OF 'l'li.E cies of sea mollusks, of reptiles, and of mamm._fetss hav~ been changed again and again, since the creta~eous era; and it is not till a long sub~equent age that we find the first traces of any other of even the humble8t species, which now exist; but here have these humble infusoria and pulythalami<l: kept the.ir place on earth through all it5 revolutions since that hme-are we to say s::tfe in lhejr very humility, which might adapt them to a greater variety of circumstances than most other animals, or are w~ 1·equired to look for some other explanation of the phenon1enon ? All the ordinary and more observable orders of the in .. habitants of the sea, except the cetacea, have been found in the cretaceous formation-zoophytes, radiaria, mollu ... ks, crustacea (in great variety of species,) and fishes in smaller variety. In Europe, remains of the marine saurians have been found; they may be presumed to have become e .. tinct in that part of the globe before this time, their place and d structive office being perhaps supplied by cartilaginous fishe , of which the teeth are found in g-,·eat quantities. In America, however, remains of the plesiosaurus have been discovered in this part of the stratified serie . The reptiles, too, so numerous in the two precedino- period", appear to have no\v much dimini~hed in numbers. One, entitl d the mosc:esaurus, seems to have held an interm0diate place between the monitor and irrnana, and to have Leen about twenty-five feet long, with a tail calculatNl to as. ist it powerfully in \Yimrning. Crocodil s and turtle xi ted, and among t the fishes were some of a saurian character. Fuci abounded in seas of this era. Confervre are found enclosed in flint . Of terre trial vegetation, as of terres trial animal , the specimens in the European area arf comparatively rare, ~·endering it proba?le that there w~ no dry land n ar. 1 he rC'mams arc cluefly of ferns, com fer , and cy adem, but in the two former. cases we havf only con . and 1 a\· . There have b n discovered rnan1 pi ·c , ·of wood containin_r holes dnll c1 ~.Z the tered?, an, thu sho-. in(r that thcv hacl been long- dr11ted about 1n th1 ~ . '1C ':tn before b in~· entombed at the b_ottom. . . The scri ~ in .America corrc spondwg 1 o t.!ns, entulet' the ~:')rrucrinons and formation, presents fos~Ils generali} identical with those of Europe, not e;xcep~mg t.he fra~ m~nts of drilled wood; sl:owmg that, 10 th!s, as In earh CRETACEOUS l"ORMATION. 65 er ages, there was a parity of cond1·ti·ono .s:- • 1 l'"' ovet· a -vas t t. ,, J.Ol' arnma l.te I act of the earth's sui·face T E · t·l th · · o uropean t ep I es. e Amencan formation adds · t· t 1 d (h . a gJgan 1c one s Y e e saurodon, from the lizard-like character f ·t' teeth. o 1 s \Ve have ~een that f?otsteps of birds are considered have been d1sc~ve:·ed ~n America, in the new red sand00. . stone. Some s1m1!ar Isolated phenomena. occur in the subsequen~ formatwns. Mr. Mantell discovered some ~nes ~f buds, ap~arently waders, in the Wealden.. The immediate connexwn of that set of birds with land may acc?unt, ?f cou.rse, fur thei_r containing a terrestri~l organic relic, which the manne beds above and below did not p~ssess. In the slate of Glarus, in Switzerland, cor spon~1ng to th~ English galt, in the chalk formation, the remains ?f a bll'd have been found. From a chalk bed nr~r 1\faidst_one, hav-e likewise been exh·acted some rema. Ins of a hu?, supposed to have been of the long-winged ~V\r1mmer family, and equal in size to the albatross. These, 1t must be owned, are. less strong traces of the birds than we possess of the reptile~ and other tribes; but it must be remembered, tha~ the evidence of fossils as to the absence o~ any class of an1mals from. a certain period of the earth's his~ory, can ne;er be considered ~s 1n.ore than negative Ant~nals, of wh1ch we find no remalns In a particular for .. nmtwn, may, nevertheless, have lived at the time and it ma.y only ~ave been from unfavorable circumstandes that their ~·emain~ have not been preserved for our inspection The. single cn·.cumstance of their being little liable to b; earned dow? Into seas, ~ight be the cause of their nona. Pp.earance In o.ur quarries. There is at the same time a hm.It to uncertainty on t~is point. We see, from \Vhat remains h~ve been found 111 the whole s~ries, a clear progress tlu ough~ut, fro_m humble to superior types of being. ~Ience we d~n ve a .light as t? w~a~ animals may have exI~ ted at particular b~es, which Is In some measure indebendent of the specialties of fossilo]Qo-y. The birds are elow the ma1nmalia in the animal sgale; and ther~fore they may be supposed to have existed about the time of th.e new red sandston~ and oolite, although vre find but sh.ght .traces of. them In those formations, and, it may be sa1d, till a considerably later period. 6 |