The opening of the mouth is small, and from it the echidna puts forth its long slender tongue, lubricated with a viscous secretion, by means of which it seizes the ants and other insects on which it feeds.
Caldwell showed that it was filled with yolk, and finally established the fact that Platypus as well as Echidna is oviparous.
In common with the other monotremes, the male echidna has its heel provided with a sharp hollow spur, connected with a secreting gland, and with muscles capable of pressing the secretion from the gland into the spur.
Amongst his children by Echidna are Cerberus, the Lernaean hydra, and the Chimaera.
There are two varieties of this species, the Port Moresby echidna and the hairy echidna.
The Marsupials include the Macro pus or kangaroo; the opossums, Phalangista vulpina and P. Cookii; the opossum-mouse, Dromicia nana; Perameles or bandicoot; Hypsiprymnus or kangaroo rat; Phascolomys or wombat; while of Monotremata there are the Echidna or porcupine ant-eater and the duck-billed platypus.
Of the three-clawed echidnas (Proechidna) confined to New Guinea there are two species, Bruijn's echidna (P. bruijnii), discovered in 1877 in the mountains on the north-east coast at an elevation of 350o ft., and the black-spined echidna (P. nigroaculeata) of larger size - the type specimen measuring 31 in., as against 24 in.