A Denebian slime devil (bottom right)
A Denebian slime devil is a foul animal from the Deneb system.
In 2268, Korax said that James T. Kirk was a Denebian slime devil, an insult that offended Pavel Chekov. (TOS: "The Trouble with Tribbles"; DS9: "Trials and Tribble-ations")
Information about Denebian slime devils was displayed by the computer as an LCARS graphic in Keiko O'Brien's schoolroom on Deep Space 9 in 2369. (DS9: "A Man Alone", "The Nagus")
Background
The artwork used in the graphic is from the Denebian slime devil entry of the Star Fleet Medical Reference Manual published in 1977.
Apocrypha
The Star Trek roleplaying game manual book, Creatures describes the Denebian slime devil as a carnivorous creature, living in the swamps on Deneb V, which can digest anything from sea animals to Humans. They can vary in sizes from 10 cm to 1 meter, and can mass up to 26 kg.