Two of the best-known species of true conchs (family Strombidae) in the western Atlantic, Milk Conchs (Macrostrombus costatus) and Queen Conchs (Aliger gigas) are quite distinctive as mature snails. When reaching maturity, both species start thickening and flaring the shells’ outer lip. However, without the flared lips typical of each species. young Milk Conchs can be easily confused with young Queen Conchs.
Nonetheless, if you observe the living animals, you’ll see that they differ, among other features, by the green color of the siphon and eyestalks in the Milk Conch, different from the brown-and-white mottled pattern in the Queen Conch. And Milk Conchs have blue eyes! (Thanks to Gabriel Delgado for information and to Senior Aquarist Carly Hulse for the great photo of the live conch.)
