The white mark in the space 3, VFW, is a crescent and the white in the margin of the ventral hind wing gets wider apically. Per David's ID text on Calydna.com M. achilles would have a "pointed" white mark in space 3 VFW and the white in the margin would be narrow along it length ( not getting wider),
https://calydna.com/taxon/10815-morpho-achilles - scroll down to the "similar species" area at the bottom of the page.