Yeah that’s not a mistake it’s simply a different style. The volcano radical is the same character as the Kanji for 8 (はち） which looks like this in text:　八

Which is exactly the same as the fins radical.

The only difference is sometimes you’ll see the lid thing on the Kanji for 8, sometimes you won’t.
You’ll never see the lid thing for the fins radical.

If you’re using an IME to type in Japanese and spell out hachi in kana like はち　then hit space bar to select the Kanji for that kana, the Kanji for hachi on the menu actually shows the little lid thing, but when you select it, the lid disappears and you get: 八

It’s similar to zero in English sometime it looks like a skinny O (0) sometimes it has a little line in it.

In fact I just noticed that on this forum if you type a response and type 0, it will show a line through it, but when you submit the post, the line disappears. So that’s a really good example that I just stumbled on.

*Sigh* And now I’m editing the post because I’ve also now noticed that when I type in 八 in the reply box it doesn’t show the lid, but when I submit it, it does. >_<

So it’s exactly the same thing. I’ll post some pics that show the difference.

Aikibujin wrote:

*Sigh* And now I’m editing the post because I’ve also now noticed that when I type in 八 in the reply box it doesn’t show the lid, but when I submit it, it does.

It’s fonts. Some fonts have the lid, some don’t. Same with 入 – some fonts have a little hook on the top, while others don’t.

Essentially “volcano” tends to appear on the top of kanji, like in 分 or 公, while “fish legs” tends to appear on the bottom, like in 六 or 共. That said, neither imiwa nor denshi jisho differentiate between them at all (and I suspect that may well be true for other dictionaries too).