Attached to the day column in Plate 29_c_ and running into 30_c_ is a series which presents a difficulty I am unable to explain. The days and numerals in this case are as follows: III Ix Cauac } 16, VI; 16, IX; 16, XII; 16, (?) Kan } Muluc The red numeral over the day column is very distinctly III in Kingsborough's work, but is II, though somewhat blurred, in Förstemann's photograph. As III + 16 - 13 = VI, and the remaining numerals agree with this result, III must be correct. Adding together the pairs and casting out the thirteens, thus, III + 16 - 13 = VI; VI + 16 - 13 = IX; IX + 16 - 13 = XII; XII + 16 - 13 - 13 = II, we find the last red number, which is wanting in both copies of the codex, to be II, whereas, according to the theory advanced, it should be III. The sum of the black numerals (four 16's) is 64, while the interval between the days is 65. The only way of correcting the mistake, if one has been made, is by arbitrarily changing the last 16 to 17; but uniformity in the black numerals apparently forbids this change and and[TN-3] indicates that the variation from the usual rule must be accounted for in some other way. In reference to this series, Dr. Förstemann[292-1] remarks: The column of the days has the difference 5; the fifth sign (in this case really superfluous), that of the thirteenth day, appears in a remarkable form, apparently as an inscription on a vessel. The black figures ought to give the sum 65, but we get only 4 × 16, or 64. But this appears to be merely an oversight by the copyist, for although in the Codex Troano, also, we find 64 several times instead of 65, still this has always appeared to me merely as a sign of the great negligence of the copyist of that manuscript. Turning to the Manuscript Troano, Plate XXVIII*_b_, we find a column consisting of the four terminal days of the year, Been, Ezanab, Akbal, and Lamat, which of course have the same relation to one another as the first days. It is evident from the space that only four were intended to be given. The numerals in Brasseur's fac simile are XI; 20, 12, IV; 9, XIII; 10, X; 13, XI.