Source : Webster's Revised Unabridged Dictionary (1913)

Prototheria \Pro`to*the"ri*a\, n. pl. [NL., from Gr. prw^tos
   first + qhri`on, dim. of qh`r beast.] (Zo["o]l.)
   Same as {Monotremata}.

Source : WordNet®

Prototheria
     n : echidnas; platypus [syn: {subclass Prototheria}]