(;EJ62ICAl SURVEY X2 L 2 Al) Al X2 7 X2 9 X2 11 X2 16 PROFESSIONAL PAPER 306 PLATE 20 5 SX2 4 6 10 12 x 2x3 13 X2 14 X2 X2 15 Al -L. X2 X2 17 1 MIDDLE MIOCENE MOLLUSKS FROM GATUN FORMATION X2