Definition of "mammalia"

Of these, 600 species are mammalia, or sucklings, mostly four-footed […] .

1851, Henry Rowe Schoolcraft, Personal Memoirs Of A Residence Of Thirty Years With The Indian Tribes On The American Frontiers‎

It is undeniable, for example, that the evidence in favour of the derivation of the horse from the later tertiary Hipparion, and that of the Hipparion from Anchitherium, is as complete and cogent as such evidence can reasonably be expected to be; and the further investigations into the history of the tertiary mammalia are pushed, the greater is the accumulation of evidence having the same tendency.

1894, Thomas H. Huxley, Discourses‎