Without getting into the rather confusion series of specifications that resulted in the Albemarle, it was a development of Bristol's Type 155 which did indeed have both a dorsal and ventral turret, in this case cannon armed.
The Albermarle was initially planned to retain two turrets, though now machine gun armed, but the ventral turret was dropped from the specification before the prototype was built. Remember that the Albermarle was never configured as a bomber and that the one dorsal turret it eventually got was a manual 2 gun version rather than the originally intended powered 4 gun version.
Cheers
Steve