Meridion
noun
Me·rid·i·on
mə̇ˈridēˌän
: a genus (coextensive with the family Meridionaceae) of freshwater pennate diatoms having cuneate cells arranged in flat, fan-shaped, or spiral colonies and often causing odors in public water supplies
Word History
Etymology
New Latin, from Greek, diminutive of merid-, meris part, portion