The plastron is cartilaginous or incompletely ossified. The turtles are covered by a leathery skin, not scutes. The head and neck are withdrawn into the shell with vertical bends as with other Cryptodiroidea. The neck is quite long and the head narrow with a double-barreled proboscis for a nose. These juvenile markings are mostly lost with age.
Adults are brown-grey sometimes showing traces of the juvenile markings.
The plastron of the juveniles is a beautiful slate-grey. The spiny soft- shell gets its name from the cone like projections on the leading edge of its carapace. The smooth soft-shell gets its name because to a large degree it lacks the spiny protuberances of its relative. Smooth soft-shells have faint markings as juveniles on a tan carapace with light colored markings on the side of the head. Adults often develop a darker mottled brown color on the carapace.