I had freshly-terminated sea urchin at Shijo's (daily special, not always available). The urchin was unlike Santa Barbara urchin, French urchin, or other urchin I have seen the shells of.
We were advised that the sea urchin originated from British Columbia waters. It was about the size of six Brittany urchins with respect to exterior shell (spiky, of course), and the single BC urchin yielded about six to eight "regular" uni that one might find on top of a piece of sushi. The price was around Canadian $24 for each urchin.
The outside of the urchin was a unbelievably intense purplish black, with spikes in the same color. Where the spikes joined the shell, there were areas of a reddish color. A very interesting-looking urchin, and one that makes me want to try different urchins throughout the world.
The taste was not that dissimilar to that of regular uni, but slightly milder. The fresh urchin was special (in terms of just having sampled it, not in terms of the taste), but the remainder of the sushi was only appropriate. The yellowtail belly sashimi was quite good. We drank Yoshi, an organic sake.