Bran`chi*os"te*gal (&?;), a. [Gr. &?; gill + &?; to cover: cf. F. branchiostège.] (Anat.) Pertaining to the membrane covering the gills of fishes. -- n. (Anat.) A branchiostegal ray. See Illustration of Branchial arches in Appendix.

&fist; This term was formerly applied to a group of fishes having boneless branchiæ. But the arrangement was artificial, and has been rejected.