Worth a visit as well is The Booth Museum of Natural History, which is a little bit away from the centre of Brighton. It's mainly stuffed birds and animal bones in a 'vintage' setting. It doesn't have much of a prehistory collection but what there is is fascinating.
http://www.brighton-hove-rpml.org.uk/Museums/boothmuseum/Pages/home.aspx
http://www.geograph.org.uk/photo/2542504
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