I should not have left dangling anyone who really is interested (OK, no one!).
Neither of those guns has notches in the cylinder; the hand does double duty to both turn the cylinder and lock it in place, using the ratchet. Since there are no cylinder notches, the flutes were carried well to the rear ("long flutes").
One interesting sidelight is that after the Model 1878 was discontinued, Colt used up left over Model 1878 cylinders on the SAA by cutting cylinder notches. These are the scarce "long flute" Single Actions, made c. 1915.