I'm not actually sure whether this is mapping anything or whether it's just a graph of some sort. Either way, I like the coloured blocks used in combination with data. I also quite like that it exists on a black background with the information reversed out. I don't particularly think this would suit the identity of the Natural History Museum, but still it's an interesting aesthetic.

This key looks as though it's come from the 1940's. The separation between the legend/index is pretty interesting. This kind of aesthetic is really interesting but it's too dated for NHM, if I were to design in a ironic/old sort of way I think I'd need to push it to an extreme since the NHM is famous for how old the majority of their collection are. To have something that resembles 1940's and present it as 'old' would, to me, seem like a joke.