The article presents an analysis of several images in Mathura art, particularly those of a goddess with serpent-like legs. They are often called tritons, which is completely wrong. These images are quite rare. To understand them, the authors turn to the religion of nomadic Iranian peoples who inhabited Eurasian steppes. The analysis of information offered by ancient authors (especially Herodotus) and that of Greek-Scythian art leads to the conclusion that a goddess with serpent-like legs is a chtonic deity symbolising the Scythian land itself. There are reasons to assume that a similar goddess was also present in the pantheon of Saka who brought this character to India. The pieces of art with the same character found in Gandhara could be an intermediate stage between Mathura and the nomadic world.