hooded seal

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A seal (Cystophora cristata) of northern seas having a grayish spotted coat, the male of which can inflate its flexible nasal cavity into a large black hood and can also inflate a nasal membrane into a red balloonlike structure.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun An arctic seal, Cystophora christata, notable for the fleshy bulge on its forehead and nose.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun medium-sized blackish-grey seal with large inflatable sac on the head; of Arctic and northern Atlantic waters