According to Roger Morris in his fine book "Atlantic Seafaring: Ten Centuries of Exploration and Trade in the North Atlantic," The Bounty was a "collier-cat" originally used to haul coal. Cat boats were smaller than Naval Frigates, the merchant ship the "Pink" and the "Hagboat"(a civilian version of the Frigate). All these designs apparently originated from the Dutch "Fluyt" or fly-boat as the English called them.
The cat was square-rigged, about 134 foot in length and 34 feet in breadth. Apparently Cats were very maneuverable: handy for crowded ports of the time. Captain Cook's vessels -- Endeavour, Resolution and Adventure -- were all Cats.
I'd be interested in learning more about the entymology of the Cat: something to do with its performance?
Cheers,
Armchair Seafarer,
Brian