There are a 5 species of large round stingrays, which are all known locally as bull rays.
They are all dark with a light underside. If the tail is used as an identifier, remember that parts can be broken off.

Pastinachus sephen Forskkal 1775
Cowtail Stingray, banana tail ray

The Cowtail Stingray can reach 1.8m across but it is usually smaller in Australian waters. Its body is wider than it is long. It is named for the deep fin like skin fold below its long tail.

Taeniura meyeni Muller & Henle 1841
    (Syn.Taeniura melanospila)

Black-spotted Stingray

Grey with black spots, or black and white mottled, no thorns, white margin, deep skinfold to tip of tail. Bottom feeder, eats crustaceans and molluscs.(pictured above)

Taeniura meyeni   Black-spotted Stingray

Dasyatis brevicaudata Hutton 1875
Smooth Stingray

The smooth stingray is the largest stingray, being up to 2.1m wide. It has no thorns on the head or back but does have a row of white pores on either side of the head. The tail is shorter than the disc width.

Dasyatis fluviorum Ogilby 1908
Estuary Stingray, brown stingray

The estuary stingray, is a smaller ray growing to a maximum width of 1.2m. It has a very long tail, with no skinfold. There are enlarged denticles along the midline and tail.

Dasyatis thetidis Ogilby 1899
Black Stingray, thorntail ray

The black stingray is about 1.8m wide, similar in appearance to the Smooth Stingray, but differs in that it has short tubercles on top of the head, in the middle of the back and on the tail. The tail is longer than the disc width.