is used indifferently for the earlier pasteboard as well as for millboard. Leather is mostly calf. Quiring is given only when the quires are in some way expressly indicated in the MS by the scribe or by a binder. The MSS with standard Library bindings are all rather tightly bound, so that refraining from giving further specification when there were no written indications saved time as well as bindings. For MSS with quire marks a complete representation was attempted : a formula such as 3 3V(33) V-l(42) IV+1(51) etc. means : three random leaves; three quires of five sheets each, the last leaf of this group being fol. 33; a quire of five sheets with one leaf missing, the last leaf being fol. 42; a quire of four sheets with an added leaf, last leaf being fol. 51, etc. Obvious quire divisions which are not indicated in such MSS are given between square brackets. For catchwords the general rule is taken to be the occurrence of catchwords in the lower margin of each verso leaf. Deviations from this rule are stated. When quires are stated to be indicated by catchwords this implies the absence of the usual catch words unless expressly stated. An earnest attempt was made to include the watermarks of the paper MSS in the description. This complex procedure however, proved to be too comprehensive for the necessarily limited scope of the Supplement. After ample deliberation and several fruitful samples the attempt was reluctantly abandoned. Similarly, but with exceptions, marginal and interlinear notes and notes on the blanks and fly-leaves are not mentioned, though clarification and even occasional rectification of Steinschneider’s description might have been useful. It goes without saying that this part of our work cannot be used without constant reference to Steinschneider’s catalogue since it only strives to fill codicological gaps in his descriptions. The third part of this volume consists of a full description of all Hebrew MSS and fragments in the possession of the Leiden Library not already described by Stein- schneider. In the description of these MSS the same rules are followed as in the Supplement, but here, obviously, the codicological part had to be followed by a representation of the contents, a task which in such a widely-diverging range of subjects and materials was not easy to fulfil in a well-balanced way. The presence among these MSS of a large collection of liturgical poetry set the author the task of solving the problem of adequately describing the poetical materials. In this case it was thought fit to follow the most generous course by quoting all the incipits. As a result not only other liturgical texts were treated likewise, but also MS Seal. 4, a volume of Selifiot of no less importance. Its contents were fully inventorised, in order to avoid too great a discrepancy in the treatment of such closely related materials, even though the MS belongs to those already described by Steinschneider. The results of this relatively close attention paid to poetical texts are laid down in an Index of Poetry at the end of the volume. The Hebrew MSS of the Leiden University Library all have two press-marks. One is the serial number (Or....) which should be used in correspondence with the Library