Dictionary of Ichthyology  

tholichthys stage = postlarval stage of Chaetodontidae and Scatophagidae characterised by large bony plates extending onto the body from the head which is itself encased in bony armour and often by silvery colour. The tholichthys plates are lost during the juvenile stage.

Forcipiger longirostris from Kendall and Goldsborough's "The Shore Fishes".  Photograph by Brian W. Coad.

Canadian Museum of Nature