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
Siege of Massilia
About the same time Massilia also submitted. With rare energy the Massiliots had not merely sustained a siege, but had also kept the sea against Caesar; it was their native element, and they might hope to obtain vigorous support on it from Pompeius, who in fact had the exclusive command of it. But Caesar's lieutenant, the able Decimus Brutus, the same who had achieved the first naval victory in the Atlantic over the Veneti,(19) managed rapidly to equip a fleet; and in spite of the brave resistance of the enemy's crews-- consisting partly of Albioecian mercenaries of the Massiliots, partly of slave-herdsmen of Domitius--he vanquished by means of his brave marines selected from the legions the stronger Massiliot fleet, and sank or captured the greater part of their ships.
19. Cf. V. VII. Venetian War ff.
When therefore a small Pompeian squadron under Lucius Nasidius arrived from the east by way of Sicily and Sardinia in the port of Massilia, the Massiliots once more renewed their naval armament and sailed forth along with the ships of Nasidius against Brutus. The engagement which took place off Tauroeis (La Ciotat to the east of Marseilles) might probably have had a different result, if the vessels of Nasidius had fought with the same desperate courage which the Massiliots displayed on that day; but the flight of the Nasidians decided the victory in favour of Brutus, and the remains of the Pompeian fleet fled to Spain.
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Reference address : https://www.ellopos.net/elpenor/rome/5-10-brundisium-pharsalus-thapsus.asp?pg=45