Fish ID???

While cleaning sea bass today, 2 of them had this flat, 4" fish in their guts. Definitely not eels as the are not round, nor have the same mouth structure. Based on the mouth structure and musculature, I have an idea, but my idea is a fish that lives way offshore and these sea bass were caught inshore, and must have dined on this delicacy within the past 12 hours based on the lack of digestion.

OK Ichthyologists, what's my new BSB bait of choice???