Motion to Dismiss (Rule 33) vs. Motion to Dismiss (Rule 16)

What's the different between a motion for demurrer to evidence under Rule 33 (which is, actually, a motion to dismiss) and a motion to dismiss under Rule 16?

After the plaintiff has completed the presentation of his evidence, the defendant may move for dismissal on the ground that upon the facts and the law the plaintiff has shown noright to relief. If his motion is DENIED, he shall have the right to present evidence. If the motion is GRANTED but on appeal the order of dismissal is reversed, he shall be deemed to have WAIVED the right to present evidence. (Rules of Court, Rule 33, Sec. 1.)
A demurrer to evidence is differentiated from a motion to dismiss in that the former can be availed of only after the presentation of plaintiff’s evidence while the latter is instituted as a general rule before a responsive pleading is filed.