Megapallifera is a slug family endemic to eastern North America.
External: Medium-large slugs (Fairbanks 1998); chevron banding pattern on mantle (Fairbanks 1990); grey or white foot margins (Hubricht 1956); one-part sole (Webb 1950).
Internal: Ribbed jaw, with 10-16 ribs (Hubricht 1956); no dart or dart sac; tubular penis without sheath; apical chamber in penis, separated by a constriction from the rest of the interior; pustulose pilasters (ridges) in penis; muscular retractor on apex of penis, and no accessory muscle at penis base; rounded spermatheca with a duct that widens toward its base and has internal wrinkles; pilaster occurring between vagina and atrium; atrium with upper and lower sections, the lower with a glandular tissue surrounding, the upper section with retractor muscles attached; internal surface of atrium smooth and with 2 lobes inside upper atrium (Webb 1950; Hubricht 1956; Fairbanks 1990, 1998).
Species identification features: Mantle patterns (e.g. gray to brown, variation in chevron distinctness), color of atrial gland, folding of inner atrial lobes (Fairbanks 1990).
Similar externally to Philomycus and often confused with the genus b/c large and with similar banding (Hubricht 1976).
About 80 mm long (Fairbanks 1998), to 100 mm long extended (Hubricht 1956).
Eastern North America (S Ontario to Georgia and Louisiana, W to Texas, Missouri, and Illinois) (Burch 1962; Hubricht 1985; Grimm 1996).