Please note that Mommsen uses the AUC chronology (Ab Urbe Condita), i.e. from the founding of the City of Rome. You can use this reference table to have the B.C. dates
From: The History of Rome, by Theodor Mommsen
Translated with the sanction of the author by William Purdie Dickson
In this character, as a purely formal right, the confirmation of the decrees of the people still continued in the hands of the nobility down to the last age of the republic.
The clans retained, as may naturally be conceived, their religious privileges longer. Indeed, several of these, which were destitute of political importance, were never interfered with, such as their exclusive eligibility to the offices of the three supreme -flamines- and that of -rex sacrorum- as well as to the membership of the colleges of Salii.
On the other hand the two colleges of Pontifices and of augurs, with which a considerable influence over the courts and the comitia were associated, were too important to remain in the exclusive possession of the patricians. The Ogulnian law of 454 accordingly threw these also open to plebeians, by increasing the number both of the pontifices and of the augurs from six to nine, and equally distributing the stalls in the two colleges between patricians and plebeians.
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Reference address : https://www.ellopos.net/elpenor/rome/2-03-equalization-orders-aristocracy.asp?pg=22