Tenor clef - Note that the bottom of the tenor clef (and thus the middle of the clef) is raised one barline off the bottom line. If you are still unsure of the difference between alto and tenor clef, notice that on the figure of the alto clef the clef extends across all 5 barlines, but here it only appears to extend across 4 barlines, being that it is raised one up from the bottom. (Yes, that black line at the bottom of the figure is a barline.)