All of the following are listed in Chambers Dictionary...
nacre (shellfish), nag (horse), naga (snake), nagapie (lemur), nagor (antelope), naiad (mayfly), naja (snake), nandi (bear), nanny (goat), nannygai (fish), narwhal (whale), native (oyster), natterjack (toad), nauplius (shellfish), nautilus (shellfish), neat (cattle), neddy (donkey), nematode (worm), nemertinia (worm), nene (goose), neopilina (mollusc), nereid (worm), nerite (snail), nerka (salmon), nestor (parrot), nettlefish, neuropter (insect), newt, night + churr/hawk/heron/jar/owl (all birds), nightingale, nilgai (antelope), noctilio (bat), noctua (moth), noctule (bat), notodonta (moth), notornis (bird), notorcytes (mole), nototrema (toad), nowt (cattle), numbat (marsupial), nun (pigeon), nurse (shark), nutcracker (bird), nuthatch (bird), nutria (coypu), nyala (antelope), nymph (insect).