The Collaborative International Dictionary
Infrabranchial
Infrabranchial \In`fra*bran"chi*al\, a. [Infra + branchial.] (Zo["o]l.) Below the gills; -- applied to the ventral portion of the pallial chamber in the lamellibranchs.
Wiktionary
infrabranchial
a. (context zoology English) Below the gills; applied to the ventral portion of the pallial chamber in the lamellibranchs.