um·bil·i·cus 
(ŭm-bĭlĭ-kəs, ŭm′bə-līkəs)
(ŭm-bĭlĭ-kəs, ŭm′bə-līkəs)n. pl. um·bil·i·ci (-sī′)
1. See navel.
2. Biology A small opening or depression similar to a navel, as the hollow at the base of the shell of some gastropod mollusks, one of the openings in the shaft of a feather, or the hilum of a seed.
[Latin umbilīcus; see nobh- in the Appendix of Indo-European roots.]