That looks superb, CBM, though being a bit of a chilli fiend and long-time grower of the things I'd say that SteveyG's suggestion above that they're scotch bonnet (habanero) is correct.
I could of course be mistaken, and it's true that there are many varieties, but I grow a lot of naga chillis and they all have the same characteristic shape and gnarled appearance, as in this pic of some of my 2011 crop:

As said, I could be mistaken, but might be worth checking back with the shop you got them from?