but as the accumulation of enduring formations, rich in fossils, depends on great masses of sediment being deposited on subsiding areas, our formations have been almost necessarily accumulated at wide and irregularly intermittent intervals of time; consequently the amount of organic change exhibited by the fossils embedded in consecutive formations is not equal.
baina fosiletan aberatsak diren formazio iraunkorren metaketa, behera doazen aldeetan sedimentu pilo handiak metatzearen mende dagoenez gero, gure formazioak ia nahitaez irregularki etenik gertatu diren denbora-tarte luzeetan metatu izan dira; eta, beraz, ez da kantitatez berdina hurrenez hurreneko formazioetan lurperaturiko fosilek erakusten duten aldaketa organikoa.