Pisiform is which type of bone:
The pisiform is a sesamoid bone, with no covering membrane of periosteum. It is the last carpal bone to ossify. 
The pisiform bone is a small bone found in the proximal row of the wrist (carpus). 
It is situated where the ulna joins the wrist, within the tendon of the flexor carpi ulnaris muscle.
Pneumatic bone
Sesamoid bone
Accessory bone
Long bone