Kalmar "genus Ostrea" tana nufin nau'in haraji a cikin ilmin halitta da ake amfani da shi don rarraba rukuni na mollusks bivalve wanda aka fi sani da oysters. Kalmar “genus” tana nufin rukuni na nau’in jinsuna masu alaƙa waɗanda suke da kakanni ɗaya kuma suna da halaye iri ɗaya na zahiri. Kalmar "Ostrea" tana nufin jinsin kawa waɗanda galibi ana samun su a wuraren ruwa kuma an san su da ƙaƙƙarfan harsashi.