Monotremes are sometimes called Prototheria, in contrast with Metatheria (marsupials) and Eutheria (placental mammals).    From Wordnik.com.  [Monotremata] Reference

In the earliest stage represented by the Monotremata or Prototheria, there was no intra-uterine development.    From Wordnik.com.  [Hormones and Heredity] Reference

If these bodies are formed only in Mammals which have uterine gestation, and not in Prototheria, they cannot be the only essential source of the hormone which stimulates the development of the milk glands, since the latter develop in Prototheria.    From Wordnik.com.  [Hormones and Heredity] Reference

Prototheria, 142.    From Wordnik.com.  [Thomas Henry Huxley; A Sketch Of His Life And Work] Reference

Prototheria, milk glands in.    From Wordnik.com.  [Hormones and Heredity] Reference