Calcar

1. (Bot.) A hollow tube or spur at the base of a petal or corolla.
2. (Zoöl.) A slender bony process from the ankle joint of bats, which helps to support the posterior part of the web, in flight.
1. A spur, or spurlike prominence.
2. A curved ridge in the floor of the leteral ventricle of the brain; the calcar avis, hippocampus minor, or ergot.