The bicolor damselfish can grow to about 10 cm (3.9 in).
The head and the front half of the body are dark grey or black and the rear half is pale, usually with some yellow, with regional variations in the coloring.
The large dorsal fin has 12 spines and 14-17 soft rays.
The anal fin is also large and has two spines and 13-15 soft rays.
The bicolor damselfish can grow to about 10 cm (3.9 in). The head and the front half of the body are dark grey or black and the rear half is pale, usually with some yellow, with regional variations in the coloring. The large dorsal fin has 12 spines and 14-17 soft rays. The anal fin is also large and has two spines and 13-15 soft rays.
Stegastes partitus