Among previously unidentified chaetodontid larvae, one form is distinguished by a long, straight, or curved horn above each eye. Because of its remarkable morphology, this chaetodontid larva has been mentioned in earlier publications, but assignment to a species has been difficult. We cleared and double stained 2 specimens of this long-horned larva to document the anatomy and its possible bearing on its identification. Using anatomical data, such as 5 instead of 6 infraorbitals and the reduction in size of the endopterygoid and the ectopterygoid, we identified our cleared and double-stained specimens as members of the Chaetodon subgenus Citharoedus. Additionally, we obtained barcode sequences from ethanol- fixed specimens that identified both specimens as mailed butterflyfish (Chaetodon reticulatus), one of the 3 species of the Citharoedus subgenus. An intriguing aspect of these larvae remains the enigma of how the horns are apparently lost, and we continue to pursue this avenue of research.