Don't worry, the bicycle rider associated with this helmet (Lewis) was not eaten by this fish! ;)
Lewis spotted the ray washed up along the shoreline of Bodega Harbor while riding his bike...and he placed his helmet next to it for scale.
This is a Pacific Electric Ray (Torpedo californica). It was ~3 feet long and ~2 feet wide. It has a very distinctive shape. Here's a slightly closer view (without the helmet):
Look for a variety of features: dark gray coloration; a very rounded disc with a relatively straight leading edge; a short tail with a triangular caudal fin; and two dorsal fins (the front one larger than the back one — see next image).
In the picture below, the caudal fin is broad and triangular at the far left. The dorsal fins are located on the ridge between the rounded disc and the caudal fin (the front dorsal fin is flopped over, while the back dorsal fin is standing upright). In this image, if you look closely at the skin of the ray, I think you'll also be able to see some smaller dark spotting which is part of the coloration of the ray.
Pacific Electric Rays are endemic to the northeastern Pacific Ocean. They occur from British Columbia to Baja California, but apparently are more common south of Point Conception (preferring waters from 10-13°C or 50-55°F).
Here's a closeup of the front of the disc, showing the small eyes and the spiracles (holes just behind the eyes). Water is drawn in through the spiracles and then passed over the gills.
Pacific Electric Rays can produce powerful electric shocks — up to 45 volts! This is strong enough to "knock down an adult human." They use electric shocks to stun prey and in self defense.
I don't know how common Pacific Electric Rays are in the Bodega Bay area. Just asking around a little bit today, it sounds like they might be relatively rare here.
P.S. Alright, this last part is only for fans of the electric slide. I couldn't help it! When looking at this ray today, I was reminded of the song, Electric Boogie. Do you know it? There are several lines that are quite appropriate when thinking about this fish:
(Boogie woogie woogie)
You can't see it
You gotta feel it
Oooh, it's shocking
Now you can't hold it
But you know it's there
This song was written by Neville Livingston (a member of The Wailers) and performed by Marcia Griffiths (a member of the I Threes, Bob Marley's backup singers). If you need a refresher: