Mechanical Snail

Nov 2008
I have been reading Waterfield`s book, Dividing the Spoils, about Alexander the Great`s successors when I came across a brief reference to a "mechanical snail" of all things that was ordered to be constructed by Demetrius of Phalerum to lead a procession in Athens in the year 308 BC. Evidently this construction was even designed to excrete a trail of slime! Any Hellenistic experts on the forum who can supply more information, please?