Taeniura lymma is a coral-dwelling ray with a rounded disc, large blue ocelli and a pair of blue lateral stripes along the tail. The blue-spotted maskray, Neotrygon kuhlii and its relatives, is flatter, more angular, greyer, marked with smaller and denser spots, and has a banded rather than striped tail. Maskrays lie out on open sand far more readily, which is where a good many mislabelled images come from.
The confusion is not only pedantic. The two differ in habitat use, depth and behaviour, so aquarium and field accounts written under one name have repeatedly been applied to the other. Taeniura lymma rarely rests exposed on sand and prefers to wedge itself under coral heads or ledges.
The species also has a poor record in captivity, where it commonly refuses food. That reputation is one reason its collection for the aquarium trade attracts scrutiny alongside reef loss.