▁as ▁the ▁European ▁flat ▁o yst er , ▁is ▁a ▁species ▁of ▁o yst er ▁native ▁to ▁Europe . ▁In ▁the ▁British ▁Is les , ▁regional ▁names ▁include ▁Col chester ▁native ▁o yst er , ▁mud ▁o yst er , ▁or ▁ed ible ▁o yst er . ▁In ▁France , ▁Ost rea ▁ed ul is ▁are ▁known ▁as ▁hu î tres ▁pl ates ▁( flat ▁o yst ers ) ▁except ▁for ▁those ▁that ▁come ▁from ▁the ▁Bel on ▁River ▁est u ary ▁in ▁Brit t any , ▁France , ▁which ▁are ▁known ▁as ▁Bel ons . ▁ ▁The ▁foss il ▁record ▁of ▁this ▁species ▁dates ▁back ▁to ▁the ▁Mi oc ene ▁( age ▁range : ▁ 1 5 . 9 7 ▁to ▁ 0 . 0 1 2 ▁million ▁years ▁ago ). ▁These ▁foss ils ▁have ▁been ▁found ▁in ▁Belg ium , ▁Italy , ▁the ▁Netherlands , ▁Egypt , ▁Greece , ▁Spain , ▁the ▁United ▁Kingdom , ▁Austria , ▁France ▁and ▁Germany . ▁ ▁Description ▁When ▁m ature , ▁O . ▁ed ul is ▁adult s ▁range ▁from ▁ ▁across . ▁ ▁Sh ells ▁are ▁o val ▁or ▁p ear ▁sh aped , ▁white , ▁yellow ish ▁or ▁cre am ▁in ▁colour , ▁with ▁a ▁rough ▁surface ▁showing ▁pale ▁brown ▁or ▁bl u ish ▁concent ric ▁bands ▁on ▁the ▁right ▁val ve . ▁The ▁two ▁val ves ▁are ▁quite ▁different ▁in ▁shape ▁and ▁size , ▁as ▁the ▁left ▁one ▁is ▁con ca ve ▁and ▁fixed ▁to ▁the ▁substr atum , ▁while ▁the ▁right