GEOLOGICAL SURVEY ~10 2 8i PROFESSIONAL PAPER 306 PLATE 17 6 5 3 9 1 xi xio xi110 13 14 010 21 Xo x2 22 X10 X410 17 23W 23 28 35 39 x10 40 x41 41 MIDDLE AND LATE MIOCENE MOLLUSKS FROM GATUN FORMATION 10 x16 16 x'0l 20 71. 6 10 26 12 X10 18 X10 Rio 24 30 1 30 A xl 27 33o 33 Jo x10 25 x18 37 38 43 0 Aj 7/ xlolo 44 x10 x10 31 32 45 x10 46 x 47 xio