There are eight of them altogether, and they can be thought of as forming two rows of four.
Scaphoid (or navicular) - this bone, with the lunate, articulates with the radius of the arm.
Lunate - articulates with the radius and the capitate.
Triquetrum - on the ulnar side of the hand, but does not articulate with the ulna.
Pisiform - a sesamoid bone that lies anterior to (closer to the palm than) the triquetrum.
Trapezium - the most lateral bone of this row. It articulates with the metacarpal of the thumb.
Trapezoid - articulates with the 2nd metacarpal.
Capitate - articulates with the metacarpal of the middle finger.
Hamate - articulates with the metacarpals of the 4th and 5th fingers. It has a projection called a hook.