These two days must be taken in connexion with the 23rd and 24th of May, which are marked in the calendars in exactly the same way. The explanation suggested by Mommsen is simple and satisfactory[179]; the 24th of March and of May were the two fixed days on which the _comitia curiata_ met for the sanctioning of wills[180] under the presidency of the Rex. The 23rd in each month, called Tubilustrium, would be the day of the lustration of the _tubae_ or _tubi_ used in summoning the assembly. The letters Q. R. C. F. (quando rex comitiavit fas) mean that on the days so marked proceedings in the courts might only begin when the king had dissolved the Comitia. The _tuba_, as distinguished from the _tibia_, which was the typical Italian instrument, was a long straight tube of brass with a bell mouth[181]. It was used chiefly in military[182] and religious ceremonies; and as the _comitia curiata_ was an assembly both for military and religious objects, this would suit well with Mommsen’s idea of the object of the lustration. The Tubilustrium was the day on which these instruments, which were to be used at the meeting of the comitia on the following day, were purified by the sacrifice of a lamb. Of the Atrium Sutorium, where the rite took place, we know nothing. There are some words at the end of Verrius’ note in the Praenestine Calendar, which, as Mommsen has pointed out[183], come in abruptly and look as if something had dropped out: ‘Lutatius quidem clavam eam ait esse in ruinis Pala[ti i]ncensi a Gallis repertam, qua Romulus urbem inauguraverit.’ This _clava_ must be the _lituus_ of Romulus, mentioned by Cicero[184], which was found on the Palatine and kept in the Curia Saliorum. We cannot, however, see clearly what Verrius or his excerptor meant to tell us about it; there would seem to have been a confusion between _lituus_ in the sense of _baculum_ and _lituus_ in the sense of a _tuba incurva_. The latter was in use as well as the ordinary straight _tuba_[185]; in shape it closely resembled the _clava_ of the augur, and perhaps the resemblance led to the notion that it was the _clava_ of Romulus and not a _tuba_ which was this day purified with the other _tubae_. * * * * *