The cover to 'Terrapin Station,' the 1977 album by Jerry Garcia and The Grateful Dead. A terrapin is "a small edible turtle with lozenge-shaped markings on its shell, found in coastal marshes of the eastern US," according to the Oxford English Dictionary. Other dictionaries define a terrapin as any of a number of small freshwater turtles. Terrapins are not typically known to play the banjo or tambourine. Some do hum a bit.