The Long List of the Ents is a list of living creatures that the Ent Treebeard, and presumably other Ents as well, learned when he was young. When he first meets Meriadoc Brandybuck and Peregrin Took, he is puzzled by them because Hobbits are not in the list.
Learn now the Lore of Living Creatures!
First name the four, the free peoples:
Eldest of all, the elf-children;
Dwarf the delver, dark are his houses;
Ent the earthborn, old as mountains;
Man the mortal, master of horses:
Beaver the builder, buck the leaper,
Bear bee-hunter, boar the fighter;
Hound is hungry, hare is fearful,
Eagle in eyrie, ox in pasture,
Hart horn-crownéd; hawk is swiftest,
Swan the whitest, serpent coldest...
Half-grown Hobbits, the hole-dwellers.