ˈkäschələ, -styə- noun
or cos·tule -schəl, -styəl
( plural costu·lae -ˌlē, -ˌlī ; or costules )
Etymology: New Latin costula, from Latin costa rib + New Latin -ula — more at coast
zoology : a small ridge (as one of those that make up the sculpture of a mollusk shell)
• cos·tu·la·tion ˌ ̷ ̷ ̷ ̷ˈlāshən noun -s