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Show 2"20 l!.:XPLA NATIONS. to account fer tl1e development of one long line, but of many comparatively short ones. And, :;s I have also remarked, there is a rapidity of generation amor~gst ~he lower animals which may well suggest som~thing ltke that ''rush of life," which, if we were to Judge fro!ll British strata alone, would seem to have taken place In the earlv seas. But, fortunately, none of these speculative answers to the objection are required; for the qu~~tion first arises Does the lowest band of the Engh~h Lower Silurian; indicate, beyond all question, the point of time at which animal life commenced upon our planet? Are we quite sure that cephalopoda were amo?g the first of all earth's livino- creatures? Far from It. It has only been ascertain~d that certain comparatively small cephalopods are found as far do~n as any .other animals of inferior organization at certain spots In Wales and Cumberland. When we remember that, in modern se?.s, certain kinds of such animals haunt special places suitable for their subsistence-that we may have crustacea and mollusks exclusively at one place. and radiata (a~ corals and zoophytes) at some other, not perhaps far distant but different with respect to depth or sume other circ~mstance-'Ye can conceive that cephalopods may occur in the first fossil bands in the places which have been examined in England, anrl yet remains of inferior animals may be found by themselve~ on the same or a lower level in some as yet unexplored place not far off; so that a time-interval may there appear to allow for a progressive development. Such seems but. a reasona~ly cautious surmise, when we are told by a h1gh authonty that there are "detached Silurian districts in England, prf'senting particular changes and m.odifications, arising from difference of depth, and the var~ety of. currents, and chemical combinations in the seas In whiCh they were formed;" and that, "in consequence of. this .vari~ty ?f physical condition, .ther.e is. a corresp.ondz"':g d,~~erstty 2n. the traces of organzc life zn each sttuatwn. Wh ~t, however, places the matter beyond. doubt is, that Ill North America, where the early stratified rocks ar~ even more amply developed than with us, the highest In':ertebrated forms do not appear at the first. In the earliest ascertained fossilife1·ous strata, the Potsdam Sandstone, • Professor Phillips, Br:t.ish Association, l845. Ath~nreum'l Re\)ott • ( I LOWER 8IL URIAN FOS!lLe. the only. fossils are lingula (a brachiopodous mol usk) and .fucmds. In the next, the Calciferous Sandrocl r fuco~dal . layers, encrinital beds, and the brachiopo~se ortlus, lingula,. and bellerophon, together with ortho! cerat~, these hezng the first ex_am_ples of the cephalopoda . And In all. these cases the fossils are few and obscure • they cornp~l~e no crust.acea. It is not till we ascend to~ fourth fossiliferous sertes, Trenton Limestone that [i , ·1 become . a~undant, or that trilobit~s appea;. Pe~h:1 : even this Is ~ot the most decisively adverse view whifh could be den ved from the American fossils for lately c:U_:re ha~e been _found, in the.Green .M:ountai~s of Ver· ~~~ nt, ~hata \VhiCh, fro~ thmr metamorphic characterf it.... believed ~y .some native geoloo-ists to be inferior and o.. course an~enor to the Siluria~s, and these contain tra ~es of fu?oHis and of vermiform bodies called N ereites, the l~st being an humble form of articulata. If this be tru~, I~ would at least add materially to the grounds for hes1tatwn. before pronouncing definitely, as the Edin. b_u!~h revieWer has done, on the commencement of fossiliferous strata and the nature of the first fossils H . we must al_so rememb~r, t~at in rocks of the elde.r conet~~ nent anterwr to t~e ~Ilu1:1ans, there are limestones, held by many to be an 1nd1cahon of organic life at the places where they are found: the chemical experiments of Brac.onnot upon masse~ of these earlier rocks gave am .. moruacal and combustible. products, likewise indicative of t~e pres~nce of organic matter: in the same subsi. lurJan. regwn, "fragments, apparently orga · d res mbl f . 1 . . n1e, an . e Ing cases o In usona, '' have been detected * d In ~ohemra actual fossils have been announced ,Ean du.b wus t races of. l"fi . . . . ven I e In sub-sllunan rocks must be ad. II!Itted to be of Importance~ when we consider that the have mostly been subjected to such a deo-ree of he t y ~ould not fail to obliterate organic memori~ls, seeina ~h:~ 1t has even changed the texture of the rocks them 0 J Ftorn what lVI~. Lyell saw of the Silurian rocks in l~:~f: ca~ he finds himself call~d upon, in the most em h f rnanner, to warn geologists aO'ainst "the ha"t p a rc t t·o n, t 1t at ~•n any of these sectibo ns we have PoJ ;': I' ta · ss lu mp· tt·v ed at ttzl e l owe st stratu1n conta· inin . 1. zve y ar• a- o""gant·c · i n. the c·r u~ t o1 t h·~ ean•h ' or have d't.B covoe re'd the firsrte lmivai~nn • bctngs whtch were en~bedded in sediment." S • Anstecl·s Geology, ii., 60. |