This observation is of the Fish, rather than the Snake that ingested it (listed separately).

My colleagues and I took this photograph of an actual original and unique X-Ray (physical "hard copy") film made in the Emergency Room of the University hospital in which I worked night shifts back in 2002. It was the regional center for medical treatment of snake bites in north central Florida. This Florida Cottonmouth's (Agkistrodon conanti) coiled body, head to tail, can be measured on the original film by laying a piece of string on the image, tracing the course of the backbone. At 58 inches, or 4 feet 10 inches (147 centimeters) then, this a pretty large snake as Water Moccasins go.

What's more, one of the main reasons we X-rayed it at all was that it had clearly recently eaten something. It had a large bulge in it's stomach, down about a third of it's body length, just past its air-filled lungs that are visible on the film as well defined darker shapes. We found the bulge was a big fish with a large blunt bony skull and easily discernable swim bladder, which we thought to be a catfish (though we lacked an Ichthyologist amongst the E.R. staff of course).

I can follow the fish's spine for much of its length in the image, but lose it somewhere along the snake's lung in the extreme right of the picture. There is an interesting and distinct structure visible at the top that looks to me like a bony spine at the front of the dorsal fin. The skull is about 7 centimeters long, and the fin spine about 3 centimeters long, measured directly from the actual film. I don't know whether the loose dense material below the swim bladder represents the fish's stomach contents, or something else in the snake's stomach. The X-Ray film was 11 by 14 inches in size, so the fish must have been roughly around a foot (30 centimeters) long in total. We did not, in any case dissect the snake in the E.R.

My impression at the time was that this was most likely something like a Brown Bullhead, just judging from what I could make out of its size and shape. It would be fascinating to hear from someone more familiar with fish skeletons and anatomy. I am sure identification from an X-Ray is possible, considering what can be done with even fossil remains among experts. I will defer to anyone with more experience reading fish X-rays.

The Radiological Technician that made the actual exposure for us on film, at my request, wrote the details of the exposure for future reference on the film itself, which, though the film suffered damage when it was later stolen from my vehicle inside a locked briefcase and dumped out in a back alley and further mistreated both by the thieves and the weather, I can still read most of what he wrote with a "magic marker":
"40(or 46) MA
1 MAS
56 KV"
Are there any X-Ray Tech's out there who can confirm that that is in fact a good exposure for a big dead snake with enclosed fish?