From The Sailor's Word-Book by William Henry Smyth (London: Blackie and Son, 1867), page 465:

MALLEMAK, or Mollymauk. A sea-bird; the Procellaria glacialis, called also fulmar (which see).

[page 327:]

FULMAR. A web-footed sea-bird, Procellaria glacialis, of the petrel kind, larger than the common gull; its eggs are taken in great quantity at St. Kilda and in the Shetlands.

[Procellaria glacialis seems to be an obsolete name. My best guess is, it corresponds to Fulmarus glacialis, or Northern fulmar.]