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
They saw that everything depended on procuring a fleet, and resolved to form one of twenty triremes and a hundred quinqueremes. The execution, however, of this energetic resolution was not easy. The representation originating in the schools of the rhetoricians, which would have us believe that the Romans then for the first time dipped their oars in water, is no doubt a childish tale; the mercantile marine of Italy must at this time have been very extensive, and there was no want even of Italian vessels of war. But these were war-barks and triremes, such as had been in use in earlier times; quinqueremes, which under the more modern system of naval warfare that had originated chiefly in Cartilage were almost exclusively employed in the line, had not yet been built in Italy.
The measure adopted by the Romans was therefore much as if a maritime state of the present day were to pass at once from the building of frigates and cutters to the building of ships of the line; and, just as in such a case now a foreign ship of the line would, if possible, be adopted as a pattern, the Romans referred their master shipbuilders to a stranded Carthaginian -penteres- as a model No doubt the Romans, had they wished, might have sooner attained their object with the aid of the Syracusans and Massiliots; but their statesmen had too much sagacity to desire to defend Italy by means of a fleet not Italian.
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Reference address : https://www.ellopos.net/elpenor/rome/3-02-war-rome-carthage-sicily.asp?pg=20