Plates 18, 19,20,21, 8 groups of 4 quadricenas.

Each of these 8 detail pictures are associated with a group of day icons. They are arranged in a rythm reminiscent of a repeating cycle of drumbeats 7-7-7-7-7-7-5-5. This does not have any obvious interpretation related to natural or astronomical cycles. I have no present understanding of the 8 associated paintings except noticing that the last painting appears to be a night scene.

The icons under the first painting at bottom of Plate 18 are the icons in the first column on Plate 1. Use of the six dots to indicate included icons in each row includes the first 7 columns in this group which is associated with the painting at the bottom of Plate 18. These are the first seven days of each quadricena.

The icons under the painting at bottom of Plate 19 are the icons in the next, eighth, column on Plate 1. By use of the six dots to indicate icons in each row to include, the icons in column 8-14 are associated with the icons at the bottom of Plate 19. This includes all the second set of seven days of each quadricena.

The icons under the painting at bottom of Plate 20 are the icons in the next, fifteenth, column on Plate 3. By use of the six dots to indicate icons in each row to include, the icons in column 15-21 are associated with the icons at the bottom of Plate 20. This includes all the third set of seven days of each quadricena.

The icons under the painting at bottom of Plate 21 are the icons in the next, 22nd, column on Plate 4. By use of the six dots to indicate icons in each row to include, the icons in column 22-29 are associated with the icons at the bottom of Plate 21. This includes all the fourth set of seven days of each quadricena.

The icons under the painting at top of Plate 21 are the icons in the next, 29th, column on Plate 5. By use of the six dots to indicate icons in each row to include, the icons in column 29-36 are associated with the icons at the top of Plate 21. This includes all the fifth set of seven days of each quadricena.

The icons under the painting at top of Plate 20 are the icons in the next, 36th, column on Plate 6. By use of the six dots to indicate icons in each row to include, the icons in column 36-43 are associated with the icons at the top of Plate 20. This includes all the sixth set of seven days of each quadricena.

The icons under the painting at top of Plate 19 are the icons in the next, 43rd, column on Plate 7. By use of only 4 dots to indicate icons in each row to include, the icons in column 43-48 are associated with the icons at the top of Plate 19. This includes all the next set of only 5 days of each quadricena.

The icons under the painting at top of Plate 18 are the icons in the next, 48th, column on Plate 8. By use of only 4 dots to indicate icons in each row to include, the icons in column 48-52 are associated with the icons at the top of Plate 18. This includes all the last set of 5 days of each quadricena.

18 and 19 20 and 21 and upper 20 and 21 each have 6 dots skipped for a total of 36x6=196 icons skipped; 18 and 19 each have 4 spots for another 8 skipped or a total of 46 skipped. Five icons are illusrated on each of six Plates for a total of 30 icins illustrated. 196 +20 = 216 icons counted; a complete ritual calendar.

That is an interesting check on the count observed but it does not help to explain the strange rhythm of six sevens and two fives repeting in every quadricena of a repeating ritual calendar.