The month signs in the codices 50 21. Diagram showing engagement of tonalamatl wheel of 260 days and haab wheel of 365 positions; the combination of the two giving the Calendar Round, or 52-year period 57 22. Signs for the Calendar Round 59 23. Diagram showing section of Calendar-round wheel 64 24. Initial-series "introducing glyph" 65 25. Signs for the cycle 68 26. Full-figure variant of cycle sign 69 27. Signs for the katun 69 28. Full-figure variant of katun sign 70 29. Signs for the tun 70 30. Full-figure variant of tun sign 70 31. Signs for the uinal 71 32. Full-figure variant of uinal sign on Zoömorph B, Quirigua 71 33. Full-figure variant of uinal sign on Stela D, Copan 71 34. Signs for the kin 72 35. Full-figure variant of kin sign 73 36. Period glyphs, from widely separated sites and of different epochs, showing persistence of essential elements 74 37. Ending signs and elements 78 38. "Snake" or "knot" element as used with day sign Ahau, possibly indicating presence of the u kahlay katunob in the inscriptions 83 39. Normal forms of numerals 1 to 19, inclusive, in the codices 88 40. Normal forms of numerals 1 to 19, inclusive, in the inscriptions 89 41. Examples of bar and dot numeral 5, showing the ornamentation which the bar underwent without affecting its numerical value 89 {xiii} 42. Examples showing the way in which numerals 1, 2, 6, 7, 11, 12, 16, and 17 are _not_ used with period, day, or month signs 90 43. Examples showing the way in which numerals 1, 2, 6, 7, 11, 12, 16, and 17 _are_ used with period, day, or month signs 90 44. Normal forms of numerals 1 to 13, inclusive, in the Books of Chilan Balam 91 45. Sign for 20 in the codices 92 46. Sign for 0 in the codices 92 47. Sign for 0 in the inscriptions 93