N any marine gastropod of the class Opisthobranchia (or Opisthobranchiata), in which the shell is reduced or absent: includes the pteropods, sea hares, and nudibranchs 后鳃目软体动物
Opisthobranch molluscs后鳃亚纲软体动物
N（名词） any marine gastropod of the class Opisthobranchia (or Opisthobranchiata), in which the shell is reduced or absent: includes the pteropods, sea hares, and nudibranchs 后鳃目软体动物