BRANCHIOS'TEGOUS, adjective [Gr. gills, and a covering.] Having gill-covers, or covered gills, as a branchiostegous fish; covering the gills, as the branchiostegous membrane. The branchiostegi are an order of fish in the Linnean system, the rays of whose fins are bony, but whose gill-covers are destitute of bony rays.
Source: Webster's 1828 American Dictionary ↗ · public-domain · returned verbatim, no AI