The Dolphin (Dauphin) relates to the title of crown prince of France and to the Greek mythology of Poseidon (Roman version Neptune) The Franks, the Merovigians, claimed to be descendant of Poseidon. In a way I can verify that is true. According to the experience I had during a school trip at the French coast when I was 14.
Hebrews 8:10 King James Version (KJV)
10 For this is the covenant that I will make with the house of Israel after those days, saith the Lord; I will put my laws into their mind, and write them in their hearts: and I will be to them a God, and they shall be to me a people: