I've only seen the adults once, after a big storm, on 25 March 2011. I found pieces of them washed up on the beach. I was puzzled at first, but eventually figured out what they were, with generous help from Roger Seapy.
Roger has written an excellent description of Carinaria japonica, illustrated with wonderful pictures, at the Tree of Life web site. I highly recommend his well-written account.
If you'd like to see my pictures from Bodega Head, I'll include those below.
For orientation, here's a diagram with their basic anatomy:
Modified from McGowan, J. A. 1967. Distributional atlas of pelagic molluscs in the California Current region. CalCOFI Atlas 6: 1-218.
You can see that their shell is very small compared to the rest of the body. I didn't find any shells in 2011, so I don't have pictures of them. However, in the diagram above we labeled the protoconch, which is the larval shell, because that's what remains of the spiraled larval shell as shown in the post about the veliger last night!
I have nice pictures of pieces of the adult heteropods that include the tail with crest, and the rounded swimming fin — which is dark purple in the photo below.
Here's another example, next to a piece of Feather Boa Kelp (Egregia menziesii) for scale (below). These are large animals — up to 15 cm long.
I also have a picture of the proboscis, which is the front end:
Inside the proboscis is a radula, or file-like tongue. Heteropods are active, visual predators. Carinaria japonica feeds on doliolids, salps, and arrow worms, among other things. They'll use the radula to rasp at their prey. Here's a picture of a radula taken under a high power microscope. Note the dramatic teeth!
Although I didn't photograph any entire Carinaria japonica that day, here's the closest image I have to a complete adult (below). It's amazing to me that the veligers I showed last night, with small whorled shells and 6 long velar lobes, grow up to look like this! And although it's not a great picture, perhaps it will be useful if you ever encounter an animal like this washed up on the beach. The purple coloration was very distinctive, as were the sweeping lines of the tail. (Also note that this individual has small tubercles or bumps between the tip of the tail and the swimming fin.)
A fascinating pelagic snail that I hope to see again some day!