phaneropneumona

from The Century Dictionary.

• In J. E. Gray's classification (1821), one of two orders of Pneumobranchia (the other being Adelopneumona), having branched vascular gills on the inner surface of the mantle, and being thus adapted to terrestrial life. They chiefly belong to the families Cyclostomidæ, Cyclophoridæ, etc., and are very numerous in tropical regions.