Alpheidae is a family of caridean snapping shrimp characterized by having asymmetrical claws, the larger of which is typically capable of producing a loud snapping sound. Other common names of these species include pistol shrimp or alpheid shrimp.
http://en.wikipedia.org/wiki/Pistol_shrimp

Ο Αλφαίος από το λήμμα στον Πάπυρο.