ventral fins meaning in English

后机身下翼

The measurements used are fork length , head length , upper jaw length , snout length , length of dorsal fin base and anal fin base and the distances from the tip of snout to insertion of dorsal fin , to pectoral fin , to ventral fin and to hard margin of preopercle
此所用于分析之外部非体节形质计有：尾叉长、头长、上颚长、吻长、眼径、背鳍基底长、臀鳍基底长以及吻端到前鳃盖骨后绿、背鳍起点、腹鳍起点、臀鳍起点等11个形质。