Echidna was born of the All-Mother, Mother Earth, Gaia, who conceived her with Tartarus, the personification of the underworld.
Echidna herself was the mother of all terrors, of the Chimera, Scylla, the Gorgon (pl. xivb), of frightful Cerberus, of the Nemean lion, and of the eagle that devoured the liver of Prometheus.
She also gave birth to a number of dragons.
One of her sons was Orthrus, the dog of the monster Geryon, who was slain by Heracles.
With this dog, her own son, Echidna incestuously begat the Sphinx.
This should be sufficient to characterize the complex whose symbol is the Sphinx. ~Carl Jung, CW 5, Para 265
In the Greek tragedies the Erinyes are serpents as well as dogs; the monsters Typhon and Echidna are parents of the Hydra, of the dragon of the Hesperides, and of the Gorgon (cf. pl. xivb); they also spawned the dogs Cerberus, Orthros, and Scylla.
Snakes and dogs are guardians of the treasure. ~Carl Jung, CW 5, Para 577
What Perseus has to do with the Gorgon’s head would never occur to anyone who did not know the myth. So it is with the individual images: they need a context, and the context is not only a myth but an individual anamnesis. ~Carl Jung, CW 9i, Para 319
Geryon was the son of Chllirhoe and Chrysaor, who sprang from the blood of the Gorgon. ~Carl Jung, CW 14, Page 452, Para fn 356