What is "arculus"

Arculus was the Roman tutelary god of chests and strongboxes (arcae) (see Indigitamenta).

In entomology, an arculus (diminutive of Latin arcus, a bow or curve) is a crossvein between the radius and cubitus near the base of the wing in certain insects.

In marine biology, Arculus is a genus of the Neoleptonidae family of marine bivalve clams.