2007 Update: I found this annotation in Google Book Search, in the Northwestern University Press's edition of Moby-Dick (ISBN 0810102684):
I'm pretty sure Melville made up a dirty story and ascribed it to ancient history. Tue Jun 28 2005 21:49 PST Darmonodes’ Elephant:
This has beeen bothering me for a while. In Moby-Dick Melville uses a metaphor that includes "Darmonodes' elephant", known for its antisocial behavior. I didn't know if this Darmonodes character was supposed to be the owner of the elephant or a historian who'd included the elephant in a book of prurient anecdotes or what, so I looked him up and--nothing. The only place he shows up on the web is in copies of Moby-Dick. Did Melville make him up to avoid direct association with the elephant story?
Apparently a misreading as the name for the elephant's owner. The editors of the Hendricks House Moby-Dick... point out that it does not occur in Melville's source passages and that its form is an impossible one in Greek. The NN [presumably another edition] editors have no explanation or emendation to offer.