σέλαχος

A. the cartilaginous or elasmobranch fishes, sharks and rays, Arist. HA 505a1, 511a5, al.; ἰχθύσι σελάχεσι Hp. Morb. 2.50, etc. (Some derived the name from σέλας, because fishes of this kind emit a phosphorescent light, Gal. 6.737.)