The London British Museum Manuscript Additional 35087, hereafter referred to as London Add. 35087, is an important parchment manuscript in large octavo choirbook arrangement from the beginning of the sixteenth century. Its measurements are 19.4 x 29.3 centimeters. The manuscript contains ninety-five folios and one stub where a leaf has been torn out (f. 4).1 The last composition in the manuscript is incomplete, which indicates that one leaf is lacking at the end (f. 96). Two sets of foliation are shown: the original Roman and a more recent Arabic. Both are placed in the upper right hand corner of folio recto. The sets agree in folios 4-93. Folios 1 and 2 show no Roman figures now; folio 3 has "ii," and therefore the missing leaf probably had "iii." The Arabic numbering does not account for this missing leaf. This folio might have been assigned "4," but this number is given on the next complete leaf to coincide with the Roman "iiii." At the end, by mistake, folio 94 has "xciii" and folio 95 has "xciiii."