In snakes and amphibians, the canthus, canthal ridge or canthus rostralis, is the angle between the flat crown of the head and the side of the head between the eye and the snout, or more specifically, between the supraocular scale and the rostral scale.
In the context of snake and amphibian anatomy, the canthus refers to the angle formed by the top of the head and the side of the head between the eye and the snout, specifically at the point where the supraocular scale meets the rostral scale.