▁ ▁Ge ometric ▁designs ▁on ▁pot tery ▁of ▁the ▁e ighth ▁century   BC ▁dep ict ▁scenes ▁from ▁the ▁Tro jan ▁cycle , ▁as ▁well ▁as ▁the ▁advent ures ▁of ▁Her acles . ▁These ▁visual ▁representations ▁of ▁myth s ▁are ▁important ▁for ▁two ▁reasons . ▁First ly , ▁many ▁Greek ▁myth s ▁are ▁att ested ▁on ▁v ases ▁earlier ▁than ▁in ▁literary ▁sources : ▁of ▁the ▁twelve ▁lab ors ▁of ▁Her acles , ▁for ▁example , ▁only ▁the ▁Cer ber us ▁advent ure ▁occurs ▁in ▁a ▁contemporary ▁literary ▁text . ▁Second ly , ▁visual ▁sources ▁sometimes ▁represent ▁myth s ▁or ▁myth ical ▁scenes ▁that ▁are ▁not ▁att ested ▁in ▁any ▁ext ant ▁literary ▁source . ▁In ▁some ▁cases , ▁the ▁first ▁known ▁representation ▁of ▁a ▁myth ▁in ▁geometric ▁art ▁pred ates ▁its ▁first ▁known ▁representation ▁in ▁late ▁arch a ic ▁poetry , ▁by ▁several ▁centuries . ▁In ▁the ▁Arch a ic ▁( ), ▁Class ical ▁( – 3 2 3   BC ), ▁and ▁H ellen istic ▁( 3 2 3 – 1 4 6   BC ) ▁periods , ▁H omer ic ▁and ▁various ▁other ▁myth ological ▁scenes ▁appear , ▁supp lement ing ▁the ▁existing ▁literary ▁evidence . ▁ ▁Survey ▁of ▁myth ic ▁history ▁ ▁Greek ▁myth ology ▁has ▁changed ▁over ▁time ▁to ▁accommod ate ▁the ▁evolution ▁of ▁their ▁culture , ▁of ▁which ▁myth ology , ▁both ▁over t ly ▁and ▁in ▁its ▁un sp oken ▁assumptions , ▁is ▁an ▁index ▁of ▁the ▁changes . ▁In ▁Greek ▁myth ology ' s ▁surv